


Aberration.

by Undertrail (Levisomnous)



Category: Undertale (Video Game)
Genre: Angst, Ecto-Tongue, Ecto-dick, Eventual Smut, Explicit Sexual Content, F/F, F/M, Face grinding, Female Reader, Fluff, Heavy Petting, Horror, I will add more specific tags as I go, Kissing, Medical Examination, Oral Sex, Post-Pacifist Route, Reader Is Not Frisk, Reader has a vagina, Reader-Insert, Sexual Frustration, Sexual Tension, Slow Burn, Unintentional Teasing, Vaginal Fingering, Vaginal Sex, forgive me for my sins, puns, there's some skeleton sex in here eventually
Language: English
Status: In-Progress
Published: 2016-02-15
Updated: 2016-02-23
Packaged: 2018-05-20 19:10:38
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 12
Words: 29,060
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6021565
Author URL: https://archiveofourown.org/users/Levisomnous/pseuds/Undertrail
Summary: <blockquote class="userstuff">
              <p>You were nothing like the others.</p>
<p>You are an anomaly. And you continue to be one, even years after you helped to destroy the barrier.</p>
<p>And he sees that in you.</p>
            </blockquote>





	1. The Beginning

**Author's Note:**

> Well! I haven't written a multi-chapter fic since 2007. I really hope you enjoy it, I'm having a lot of fun writing it. It's a slow-burn, because I live for those, hopefully you won't be kept waiting for too long. (You won't, because I am incredibly impatient with myself)
> 
> Anyway! On with the show!

You had pondered it all day.

Sitting on the unsteady boat on the river, the cloaked figure hummed a gurgling melody, before speaking.

“Beware of the man who speaks in hands.”

“Excuse me…?” You voiced, questioning, and yet, as if by selective hearing, the guide said nothing to ease your growing curiosity towards the statement. 

Your time in the Underground had been met with almost constant aggression, though it was superficial and easily solved. You took pride in the fact you were a pacifist by nature. After learning the history of the monsters and the humans, you were determined to change the perception of how monsters saw humanity as a whole. It was a huge undertaking, but you were happy enough to try.

You had written it down. Scrawled against a crumpled, half torn poster of Mettaton, the words of the River Person inked against the robot’s rectangular body. You had to ask someone.

But this was years ago.

The barrier fell, and you became the swell of the news stories, tales of how you broke the seal and led the monsters to sanctity. You didn’t feel as if you were nearly as heroic, given the memories of narrowly dodging things being thrown at you and running away wherever possible. Honestly, you were content when the stories died down, being left to your own life once more. You had even managed to keep close friends. One of them currently lazing on your couch, flipping through the television channels, a fixed grin on his skull.

You had let him. The skeleton’s company was always welcome, your apartment seemed to bleed loneliness when you were the only inhabitant within its oddly sterile walls. Stifling a sigh, you flipped through paperwork and bit your lip, rolling your eyes. Bills, policies, some kind of Ambassador duties that you’d rather ignore until they no longer mattered. The job paid well, and technically, you barely had to lift a finger, feeling spoiled and ungrateful for the fact that you still procrastinated on signing work.

“lost in thought, kid?”

You jolted slightly, wilting as Sans gazed at you from over the back of the couch, finally relenting and setting the papers down on the counter, frowning deeply at them.

“Sort of. I just feel a bit...overloaded with all of this. I know, I know. I should have done it sooner. But it’s _boring._ ” You sounded like a child, but you no longer cared, hearing the soft, lingering chuckle from the couch, you trudged over, plopping yourself down by Sans’s feet.

“maybe you’re just getting off on the wrong _foot?_ ” He winked, slowly wiggling the slippers in front of you, as you reluctantly grinned, groaning as your head lolled to rest on the cushioned back.

“Actually terrible. Ugh, I feel guilty just _sitting_ here. I think, I might head to my room. At least there’s a desk, and I’m not torturing my poor kitchen counter with my work.” You fiddled with your shirt idly, mulling it over. Sans shrugged and smiled, as always, before pinprick pupils gazed over to the television.

“don’t overdo it. wouldn’t want you working yourself to the _bone._ ”

“Sans!” You giggled, slowly bringing yourself to stand as you strode to the kitchen, snatching up the work disdainfully and slipping back to hermit into your room.

Your room was plain, save for the smatterings of clothes and _more_ paperwork about your floor. As sad as it may seem, you never thought to be more personal. You had spent a good portion of your life moving from home to home with your family, never truly settling. Deep down, you felt as if perhaps it would be nice to introduce some uniqueness into your apartment. But you could only ever fall back into the same cycle of wondering if you’d want to move right after. Ugh.

You skimmed over the work, sorting them into piles. One for bills, one for human-monster relations, and an ‘other’ pile, which was for the useless bits of paper that you had not bothered to throw. Many notes and doodles covered the pages, and you chuckled softly at a few, before setting them down.

But one caught your eye.

A pink leaflet. You raised a brow curiously at it, before slipping it out. The memories caused you to grin.

“Wow...Mettaton. Back when you were just a whirring box.” Not much had changed. His new body was a whirring...pair of legs. You stifled a snort, before your smile faded, narrowing your eyes at the faded ink scribbled along the robot’s body.

“...What? ‘Beware the...speaks in hands’?” You mumbled, bewildered. It was unmistakably your own handwriting. You couldn’t recall why on earth you would have written it. You stared at the writing for what felt like centuries, scraping your mind to summon up an idea as to why you had noted something so vague and obscure down. Were you smoking dog treats at the time?

“...Sans?” You called out, emerging from your room to eye the skeleton on the sofa, who arched a brow bone slowly at you.

“what’s the matter?” His usual joking mannerisms were gone, though the smile was still plastered on his face, it seemed nervous. You fumbled with the poster for a while, before slowly shuffling over, sitting next to him.

“Can you understand this at all? I mean, it’s obviously old. I haven’t been in the Underground for years. ‘Beware…’” You started, sighing. “Something, something. ‘Speaks in hands’.” You soon finished, and Sans took the poster from your fingers, eyeing it down carefully, before nervously setting the poster onto his lap.

“where did you hear about this?”

“Well, that’s the thing. I can’t remember. Is everything okay? It’s not...it’s not bad, is it?” You worried at your lip, as Sans tensed and swallowed, phantom sweat started to bead on his skull.

“it’s not _right_ , but it’s not bad.”

“What the hell does that mean?”

“...do you know anything about someone called w.d gaster?” Sans turned to you, sitting more formally than you think you’ve ever seen him before. You searched your mind for bells, but slowly shook your head.

“No. Should I have?”

“no. that’s the problem. i dunno how you wrote this down, or what you heard to have this written, but it ain’t right.”

“Y-You’re not making any sense.” You stuttered, nerves shooting down your spine, as Sans sighed, trying to smile genuinely, only managing an odd grimace.

“sorry, pal. lemme try and fill you in. gaster was a royal scientist, like alphys. he was the one who created the core.” Sans slowly explained, watching your reactions carefully. You sat back, confused, one hand stroking through your hair, the other drumming fingers against your knee, trying to soothe your growing anxiety.

“The...core. The same one I was running around in?”

“yeah. the same one. well, here’s where it gets a little...he fell into the core. it’s speculated, so that might not have actually happened. but what did happen was that he vanished. forever. gone.” Sans gestured with his hands, and you swallowed thickly, your head spinning.

“So where does this all fit in with some stupid poster?” You stared at the pink paper, frowning, fighting a shudder, as Sans’s bony fingers stroked over the offending material.

“gaster was a genius. had a better understanding of magic than probably any of us could. he could summon his own...his own hands, to help work. used to sign to monsters. used his hands for everything. you’d argue that he-”

“Spoke with them.” You felt your chest hollow, conflicted, confused. Sans merely nodded. You were sure if he could, he’d be biting his lip. You didn’t understand. It was some kind of joke. You laughed, if only to appease your scrambled feelings.

“you okay?” Sans questioned. You nodded, snorting.

“This isn’t real. You can’t be serious, Sans! You can’t expect me to sit here and think some mysterious, _dead_ scientist still exists. Not only that, but _I_ of all people had scribbled down a message from somewhere to argue proof that this vanished person was onto me, and that I have to ‘beware’ him.” You chuckled, but Sans remained the same, smile twitching.

“maybe. do you know how you got this at all? you really don’t know why you wrote it down?”

“Nope. Maybe the spooky man himself whispered it into my ear in a dream.” You winked, and Sans laughed, though not soothed, he decided to drop the subject entirely. If only to make you comfortable. 

You had had enough, snatching the poster and ripping it up, you grasped the shreds and wandered to the kitchen, dumping the pieces into the trash, stalking back over to plop yourself back onto the couch, urging Sans to pass you the remote control to the T.V, both of you settling to watch a documentary.

Time passed. You could hear water. A soft tickling beside your ear as water lapped at your sides, but not touching you. The distant hum of a song. 

_“Beware of the man who speaks in hands.”_

_“Excuse me…?”_

The water plodded against wood, it was so calming, and yet the words raked down your flesh as if it were trying to rip you apart. 

You bolted up from the couch, eyes wide as realisation flooded into you that you had been dreaming. Sans was asleep on the other end, still and quiet, not bothered by your sudden burst. You clutched your chest, trembling. You were talking to someone on a boat, when they had told you. Your mind replayed the dream over and over, until you were losing the image and the words were nothing more than an ugly slurring. But you remembered.

You remained in the kitchen, sipping water steadily. Something about the words started to unnerve you. The idea of a dead monster still...somehow alive. You shivered. The silence of the apartment, save for the hum of the television, started to seep into your skin. 

You remembered your time in the Underground. You were just a young teenager back then. Scraggly and frightened, you braced yourself for every challenge thrown at you. You recalled blue, talking flowers, and then a rather specific talking flower. You cringed. 

Thoughts drifted. To the water. You shook your head and gulped down the rest of the water in your cup, slamming it down rather harshly, gritting your teeth. You hated that it was bothering you so much. It festered in your insides and suffocated your thoughts, until you couldn’t take the silence, feeling guilty, you strode over to Sans, shaking him awake.

His sockets shot open, pinpricks rapidly searching for the source of the shaking, before you settled him, stumbling back slightly. 

 

“s-sorry.”

“It’s fine. I...wanted to ask you something.” You paused, wondering if you should let the poor skeleton wake up first. Sans smiled groggily, settling back down, silently imploring you to continue.

“I had a dream. About being on a boat. That’s where I heard what I wrote down. I don’t know who said it, or why, though? I know it sounds stupid, but it felt like I was back underground.” You admitted. Your clothes felt tight on you, after falling asleep in them, you ached to get into something more comfortable. 

“we only had one boat in the whole of the underground. you might be thinkin’ of the river person.”

“It rings a vague bell, somewhere. But why would they know anything about...what’s his name?”

“gaster.”

“Yeah. It seems really out of place, right? For me to run around down there and have no idea about him, but this person on a boat does? Speaking of which, does Alphys know anything about him?” You patted your hips, frowning at the lack of hard edges in your pocket, before standing and searching about the room for your phone, dropping to your knees and padding under the couch, until you had it grasped in your fingers, flicking the screen and bringing it to life. As you were searching for Alphys’s name in your contacts, Sans began to speak.

“the river person says a lot of weird things. i think alphys might know, but she’s not the greatest speaker when it comes to this kind of thing. after all, she managed to hide the amalgamates from everyone.” 

You could tell Sans was still upset. There was still an awful tension between them, and truthfully, it was hard to blame him. For a long while, you had been the same. Though now, it was different, if only just.

“You don’t have to bring that up, Sans. Do you know anything about the River Person?”

“can’t say i do, sorry. they were just someone who got you around places, y’know? insisted that they didn’t even have a name worth remembering.” Sans sighed, slowly standing for the first time in over 12 hours, bones clicking and rattling as he stretched his arms above his head, his head slowly lolling to the side. You wondered how he clicked like that and didn’t fall apart, but you had to chalk it up to monster magic. Like most things related to Sans.

“...I’m gonna talk to Alphys.” You decided. It was late in the evening, and you idly plucked your phone into your hand, swiping through your contacts, before pausing, a hand on your knee.

“don’t sweat it, okay? you’re probably worrying over nothing. everything’s going _tibia_ okay.” Sans winked, and your nerves ebbed, grinning at him and swatting playfully at his hand. You had looked away, just missing the faint blue glow on his cheekbones, you leant into the arm of the chair, phone pressed to your ear.

You heard it being answered, just barely, claws scraping over the microphone as you scrunched your nose at the feeling in your ear, before a nasally ‘hello’ made its way through to you.

“Hey, Alphys, it’s me.”

_“O-Oh, hello. D-Did you need something?”_

“Well...sort of. I’m wondering if it’s something I really wanna talk about on the phone.”

You heard her fumbling, nervously, and sighed. Everything was happening so quickly. You were only rushing it to rid yourself of the ugly ball of nerves in your throat. It didn’t feel like something that could be swept away, like those papers. After a moment, Alphys cleared her throat.

_“W-Well, i-it’s pretty late. M-Maybe we could arrange something tomorrow?”_

“...Yeah. Okay. Let’s meet for some coffee!” You tried to sound optimistic, but the thought of waiting had you nervous. You were always impatient with these kinds of things. You offered her a goodbye, hanging up, sighing loudly as you slumped over the arm of the couch. Sans had been quiet the whole time, and you shot him a look, wondering if he had dozed off, surprised to see him watching you.

“not to sound like a _bonehead_ , but you look really worried about this.”

For a while, you said nothing, letting time trickle by as the seconds stretched. You smiled weakly at the joke, but your thoughts were otherwise occupied.

“Yeah. This all started because I decided to look at some dumb poster for Mettaton. Can you believe it? I don’t even know why I’m so bothered by it, actually.” You shrugged, sighing, snagging the remote and changing the channel to something else, something that played all night. You set the little control down by your feet, huffing a short breath.

“why _are_ you bothered about it?” Sans had to ask. You absentmindedly stroked your arms.

“...It seemed so harmless. What I wrote. Maybe a little weird. But you reacted like you’d seen some kind of deadly premonition. We’ve been out of the Underground for years, Sans. What I wrote down was years old. But the way you spoke about it made it sound like I was in danger. Like I was about to be experimented on by some mad scientist.” You babbled uselessly, and drank in the silence that followed, the faint voices on the television offered some comfort, at least.

“i didn’t mean to make you have a heart attack, bu-”

“Hey, come to think of it, why were you so nervous about it?”

“w-what?” Sans tensed, smile faltering for a second, before he laughed. “i wasn’t nervous. just a little freaked out. i wasn’t expecting it to even come up.” 

“...Wait, something doesn’t make sense. You instantly knew what I was writing about. About...Gaster. It could just be that he was famous, but-” You were cut off, Sans’s phone buzzing loudly in his short’s pocket, he grinned at you and stood, taking out the phone and answering the call, careful not to look at you.

“hello? hey, papyrus. yeah, i’m at- okay, i’m comin’. be home soon.” Sans shrugged, smiling, turning to face you. You threw him a look, rolling your eyes in return.

“Guess I’ll never know. You wanna come to coffee with me and Alphys?”

“nah, i’m good. text me what you find out, though, yeah? i wouldn’t wanna call you out for hiding something from me.” He beamed, and you snorted, caught off guard, your negativity draining as you stood up to lead him to the door. 

You didn’t want him to leave. You didn’t want the silence. But you understood, as he paused at the door, you wrapped your arms around him tightly, feeling him chuckle against you, his hands slipping to your sides to let you pull back. 

“Nice blush.”

You grinned, as Sans blinked, clearing his non-existent throat and swinging the door open, fixing a smile and leaving with a noncommittal wave.

You felt the quietness along your spine. Looking around for some kind of relief, you figured you would take a shower, to ease the crawling on your skin.

The water was pleasant, you sighed in satisfaction as fat droplets of water rolled along your body, enjoying the feeling of massaging the shampoo into your hair. Something in you wanted to get yourself off, calm you down. You weighed up the idea but decided that it wasn’t worth the effort. You’ve reached a new level of laziness.

You barely wanted to put on clothes to sleep in, settling for panties and an old shirt, yawning, you slipped under the covers of your bed, eyeing the paperwork on the desk nearby, uttering a small groan before shutting your eyes.


	2. Understanding

Something had woken you. 

It felt like pulling. The same feeling you got when you were fighting monsters. A pulling in your chest, ugly and torturous, it had roused you from your sleep, coughing. You felt a shortness of breath, and panicked, trying not to hyperventilate as you stood, your vision swimming. It felt like something was around your neck, squeezing until the air was cut off, and you slowly had to sit back down on the edge of your bed.

The feeling had settled the longer you remained awake. You couldn’t remember the dream you were having. The window that sat behind your desk was bright, your curtains shielding you from the sun.

_Alphys._

You groaned loudly, looking for your phone, as you stood and slogged into the living room, taking your phone from the cushion and pressing the home button. 

“One missed text from Alphys. I hope she isn’t mad.” You mumbled to yourself, tired and still settling your throbbing heart, you called the scientist, wandering into your kitchen and popping the call on speaker as you poured a glass of water.

_“O-Oh, hello! A-Are we still going out today?”_

“Yeah, is that okay? I haven’t seen you in a while. It’d be nice to catch up.”

_“I-It’s fine! I-I know, I’ve been busy. Are we meeting b-by the cafe near the park?”_

“The pink one? Sure. See you there.”

You smiled, despite the fact the other end couldn’t see it. It was true. Alphys had a habit of being an introvert, more so than you, and it took a lot of effort to get her out of her home. She was lucky to have a job that she could manage from the comfort of her own computer. Although, the same was often said for you, too. You hung up, fiddling with a few apps before downing your drink and licking your lips.

You picked out a simple pair of jeans and a shirt, giving yourself a once-over in the mirror before checking the house, snagging your keys and turning the television off, striding out of the apartment and locking it, before making your way out.

“G-Gaster?”

You and Alphys sat by the giant window of the cafe. You nursed a small cup of hot cocoa, frowning at the reaction Alphys gave you, letting a huff of breath escape you, the steam from your drink shivering.

“So, you know about him, at least. You were the Royal Scientist, after all. Do you know anything more than his job? What happened to him, I mean.” 

You took a sip from the hot drink, glancing at the girl behind the counter, who smiled politely back, having caught your eye, multiple limbs focused on various tasks, and you nodded your head, before returning to Alphys, who was nervously fidgeting with her cake slice, prodding it with her fork.

“Well t-they say he fell into the Core. But they don’t know much else. It’s not as if we could have f-found a b-body.” She ended the sentence nervously, the subject matter growing grim. You swallowed thickly. The idea was unsettling.

“Right. Right…” You repeated, trailing off. There was a tense, pregnant silence between the two of you, and the scientist slowly ate the cake slice. “...Do you think he’s actually gone?”

You broke the hush, and Alphys paused in her eating to give you a nervous look.

“I-I don’t know. I think there was a r-rumour going around that he...scattered. B-But most things about Gaster were rumours.”

“Scattered how, exactly?” You asked, feeling drained from the conversation. There really was no information on it. The one person, sitting right in front of you, that could possibly know more about this mystery, only knew rumours. 

“I-It’s complicated. The theory stated that h-he somehow...vanished into time and s-space. I don’t exactly know, myself.” She hurried to clarify. You frowned, hands cupping the mug of hot cocoa, palms pressed into the warmth.

“That sounds ridiculous. Not to be rude.”

“N-No, it’s fine. Can I ask...h-how do you know about him?” 

You tensed, conflicted. It seemed stupid to have to explain, given the circumstances in which you found out.

“I...when I was underground, I think someone told me something about him. About ‘a man who speaks in hands’. I asked Sans about it, and he told me about Gaster. I don’t think I knew anything back then, either. Maybe that’s a good thing. Sans looked on edge about it.” You confessed, and Alphys smiled nervously, pushing up her glasses to sit on her snout. 

“W-Well it is a little spooky, considering h-he was long gone before you even a-arrived.”

You hadn’t considered that. You pondered over your drink, testing its warmth and taking a considerable swallow, as Alphys broke off another piece of cake and pushed it into her mouth. 

“Ugh, anyway. Enough about creepy things. How’re you and Undyne?” You smirked, and she coughed, choking on the cake piece, before erupting in a bright blush.

“W-W-We’re good!” She half smiled, caught off by the question. You hummed in acknowledgement, arching a brow, smirking.

“I’m glad. I aspire to have a relationship like yours one day.” You smiled weakly. It had been too long, since you were last dating someone. One night stands didn’t seem to personally mesh with you, and you often found your only companionship with your fingers. Inwardly rolling your eyes, you watched Alphys blush and smile warmly.

“T-That’s cute of you to s-say.” 

You had gone to speak, but the buzz in your hip gave you pause, and you slid your phone out, reading Sans’s name flash on the screen. 

“Oh, hang on a second, Alphys. Sans wanted me to tell him about...Gaster.” The name made you tense. It seemed to have the same effect on your friend, who stiffened at the mention. Your fingers smoothly tapped at the glass screen, until you were satisfied, pocketing the phone again.

The rest of the day was spent alone. After bidding Alphys goodbye, you were back in your apartment, finally sorting out a few pieces of paper. They had bothered you enough. You got through a personally impressive chunk, smiling at your efforts. It had even calmed your mind.

Sans was texting again. You sat your phone on your desk and read over the message, curious.

_‘did you manage to find out anything else?’_

You sighed. You really were hoping to. Just to ease your curious mind for a moment. You quickly typed, frowning to yourself.

_‘Nope. She essentially told me the same thing you did. Only she mentioned something about him scattering across space and time. Which made even less sense! I’m more confused than ever. :(‘_

You set the phone down again, slumping into the nearby chair, rubbing your temples. It was stupid to be so quickly obsessing over something that had no relevance to your life. It was all behind you. So why did you care so much?

A buzz. Your phone lit up, and you pulled it towards you.

_‘scattering across space and time? could she tell you more about that?’_

_‘Again, no. Everything is just...rumour. It would be nice to have some hard facts.’_

You waited. Another buzz.

_‘the facts can’t help not being hard. :(‘_

You snorted a laugh, the lewd joke had you smiling stupidly at your phone. Sans was great for calming your nerves. You almost missed him lingering in your apartment. But Papyrus was supposed to be cooking today. Someone had to make sure the house didn’t burn to the ground. 

_‘I’ll be sure to be more sensitive. ;)’_

You typed quickly, chuckling to yourself. You almost wanted to pat yourself on the back for such cunning wordplay, but perhaps it was better that you didn’t. 

Time oozed by as you lingered around the living room. The television was fine, for a while. But then the thoughts came in. Small waves, at first. What ifs and theories springing up and settling soft snow. It grew, until you were curled up beside the arm of the sofa, biting your lip.

You had even tried to research the idea of space and time on Google, but felt immediately out of your element, grimacing as you flung the app closed. There truly was nothing. There were no archives of newspaper from the Underground about the situation, no person to ask, save for the River Person. But they had long gone. The world was too big to go hunting them down. 

The whole thing was utterly hopeless. Yet the nagging continued as if by some divine recollection you would scream eureka and suddenly be blessed with the answers you so desperately wanted. Idiotic.

By the time that you had eaten, night had long fallen, and you perched yourself by the living room window, staring up at the sky. 

“What are you _hiding_ from me?” 

You spoke, so slowly, a small voice among the pollution of the television. Tired eyes swept over the expanse of the stars. You wondered if it would be worth taking comfort in Sans, or even Papyrus. Maybe Undyne. But it was late, and knowing them, they were in the comforting hold of their beds. Whilst you moped about a potentially incredibly dead scientist. Incredible.

It had taken you over a week to decide what you were going to do. Fire burned in your stomach, bundles of anxiety made you want to throw up, as you paced about your apartment nervously.

You were going to return to Mount Ebott.

There had to be more information inside the Underground. It wasn’t as if it was some kind of illegal, ruinous place. It was, however, abandoned. You pulled on the fabric of your shirt, your timorous gaze on the floor as you thought it over.

Would it be worth it?

To return after all those years. You swallowed, and clenched your teeth. You asked Sans to come over, to tell him in person. You almost wanted him to stop you.

“if i thought you looked worried before, you definitely look worried now.” Sans chuckled in worry, smile strained. Behind him stood Papyrus, who loomed almost comically over his brother.

“Human! I hope you do not mind that I, The Great Papyrus, has joined my brother in visiting you!” The skeleton stood proud, and you smiled, albeit halfheartedly.

“No, it’s fine, Papyrus,” You urged them both to sit on the couch, your hand fiddling with the phone in your pocket as you sat gingerly beside Sans, letting out a small breath. “I’m going back to Mount Ebott. Don’t!” You shushed Sans as he opened his mouth, watching him slowly close it with a soft clack.

“I want to go. It’s abandoned, right? So I won’t be in much danger. I’ll take my phone, just in case. I have to know, Sans. It’s eating me alive not knowing. Everything about this guy is suspicious.” You felt both of the brothers gazing at you, not willing yourself to return the stare, keeping your eyes lowered to the hands in your lap.

“then let-”

“You’re not coming with me. Either of you. I’m not going to risk anything, Sans. It may be empty but it might not be the safest.”

“Human! I would personally like to know what it is you are returning to the mountain for!” Papyrus half whined, fidgeting in his seat, gloved hands patted his knees as he leaned forward to direct his attention onto you. You tensed. Of course he didn’t know. You glanced to Sans, silently asking, but Sans shot one back. Clearly, Papyrus shouldn’t know.

“I...I left something behind in there. It’s important to me. I think a suspicious guy took it.” You lied through your teeth, feeling horrible for the poor skeleton, who nodded wisely.

“I see. Well, in that case! I believe you should retrieve it!”

“I agree. Sans?” You eyed him carefully, smiling smug as he fought a frown, grinning in return, though his gaze dropped. He looked upset.

“don’t get too _bonely_ without me.”

“ _Sans!_ ” Papyrus yelled, bolting up from the couch and casting Sans an accusatory stare. You giggled, trying to soften the heavy mood.

“hey, papyrus? you think you could go to the car and grab my phone for me?” Sans looked towards Papyrus, who visibly mulled it over, before relenting, flinging his scarf over his shoulder and holding a hand over his ribs.

“The Great Papyrus can do _anything!_ ” With the statement, he was already darting out of the door. Once the latch clicked shut, you were alone with Sans, and the air grew tense and uncomfortable.

“don’t do it. it’s not worth riskin’ yourself for rumours. gaster’s long gone.”

“Alphys made a good point, the other day. She said that he was long gone by the time I arrived. But the River Person still spoke about him. Either the River Person is painfully old, or...I was being genuinely warned.”

“don’t you think if you were being genuinely warned, it would give you even less motivation to go? what if you get hurt?” Sans looked genuinely concerned, his smile faltered as the pinprick pupils in his sockets throbbed strangely. You frowned, taking his skeletal hand in your own, feeling smooth, thick bone against your palm. He attempted to stifle the hitch in his breath, the glow on his cheeks, turning his head and remaining angry.

“I’ll be okay. Please, trust me on this? I know the layout well enough. I just need to find out something. _Anything_. Aren’t you curious at all? Why was I warned even though Gaster’s been dead for so long? How did he really die? Did he even die at all?” The questions blurted from your lips, and Sans squeezed your fingers gently, pinpricks looking up into your own eyes. He loved that passion in you.

“...call me or text me every day, just so i know. i need you to _patella_ me you’re doing okay down there.” He slowly stretched his grin at you, and you let go of his hand, pushing his shoulder and laughing softly.

“Okay, I’ll call. Those puns are absolutely awful.” You smirked, and he chuckled, before the door slammed open, and Papyrus was storming in, thrusting the phone at Sans.

“Here!” He called in triumph, grinning. Sans took the phone and smiled at it, before grinning warmly at Papyrus.

“thanks for bein’ so cool, bro.”

“I am _always_ cool!” 

“yeah.” Sans laughed, standing, waiting for you to join him. You lingered for a moment. Standing, you gave an awkward glance around.

“I’ll leave home tomorrow morning. So I get as much daylight as possible on my way up. I’ll text before I go, okay?”

“...okay.” Sans replied, with a stifled sigh. You could see him strain to smile, but would not question it. Papyrus had wrapped his arms around you, his ribs pushing against your own as you wheezed, before patting his spine in return.

“Be safe, human! I hope you find what you’re looking for!” He laughed, pulling back, and you smiled, as the two brothers left the apartment.

“...Me too, Papyrus.”

**Notes for the Chapter:**

> Ooh, finally. Things are actually moving forward!
> 
> Your Kudos is absolutely appreciated, thank you very much!
> 
> (PS: You can bug me on Tumblr @undertrailingbehind!)


	3. Abrading

The morning rolled around, your phone buzzed in your ear as the alarm sounded, ripping you from your sleep as you slowly sat up, knocking your fingers into the glass in a desperate attempt to shut the thing up.

You had almost forgot entirely about your journey. You stumbled into the shower, cleaning yourself with a loud yawn, slinking out and drying yourself off. The thoughts started to trickle in. You were really going back to the Underground, for the sake of your own curiosity. You couldn’t decide if you were truly that stupid. Apparently so, you mentally shrugged it off as much as you could, picking comfortable clothes and shoving them on.

You had no idea what to bring. You were pleased to have the luxury this time, thinking back to the years ago when you had fallen. You took a backpack, bringing a portable phone charger, a sleeping bag, and small amounts of food. You weren’t planning on staying long. A week at most. Just enough. 

You took your phone from the bed, stroking over the back carefully. Pressing a button, the screen lit up. Missed messages tightened your chest, and you worried at your shirt.

_‘hey. text me when.’_

_‘Hey Sans. I’m on my way now. Wish me luck, bonehead! :)’_

You had to smile. Otherwise you felt as if you’d bawl out of nerves alone. You wondered how much had changed, slinging the backpack behind you, the straps resting on your shoulders. Would it all be a gigantic, towering mass of claustrophobia, like you remembered as a teenager? You laughed stiffly as you locked your apartment door, staring down the hallway, you breathed deeply. 

You took the bus to the outskirts of the city. From the stop, you could make out Mount Ebott. You retraced your steps along the path, until the concrete was replaced by dirt under your feet, the trail vague and grassy. You were being chased, that day. Bullies from your school were scaring you up the mountain, and you bolted fearfully up to the very top. You couldn’t see them, but you were paranoid enough to hear them laughing at you. Until you fell.

You sighed. It was a bitter memory. It wasn’t even worth recalling. Ironically, the same could be said for this entire trip.

The hole was monstrous. Like a waiting maw, wide and open, you peered inside to see the distant yellow of flowers. Surprisingly, the climb had been made much easier thanks to humans. Ropes were pulled into a makeshift ladder. As soon as you had emerged, breaking the barrier, humans were frantic to discover the insides of the Underground. It made the journey less hassle. It beat falling down.

You had gotten down. It felt so much colder down here. The flower petals wiggled in the draft, and the nostalgia ran through your body. 

“...You’re back?”

The voice startled you. A single flower blossomed, a face staring up at you as you slowly crouched to the ground, a sad smile on your lips.

“...Hey. I’m not sure what name I should call you…” You admitted. The flower half sneered at you.

“Flowey. What’re you doing here? Unhappy with something? You’re...not planning on resetting, are you?” His face twisted into a sad, pathetic smile. You shook your head. You had been through enough. No resets. It was a promise you had made to Sans on getting out. It was a promise you had made to _everyone_. 

Flowey seemed more relieved, swaying on his stem.

“So then, why _are_ you here? There’s no one left in there.”

Your finger stroked petals. Flowey attempted to snap onto your skin, but you moved, frowning.

“I’m...trying to figure something out. Ah, do you know anything about someone called...Gaster?”

“Nope,” The reply came quickly, and you frowned. Flowey seemed to pull a face with you. Thin vines crept along your wrist, squeezing. “Is it...nice out there?”

You felt a pang of guilt for the flower. You knew better than to hate him. Even after it all, he was such a small, sad thing. He pulled your finger closer, letting it brush along his petals.

“It is. Monsters had a hard time getting along with humans. Humans aren’t the easiest to win over, not even with each other. It’s been hard, but...I think it’s going to be okay.”

Flowey pondered, thin vines left your flesh, leaving scratches in their wake, as you returned your hand to your chest. You stood up, knees clicking as you looked down at the flower, who craned their head up to look at you, a sad, tired smile on his face.

“N-No resetting, okay? I’m too tired to do it again.”

“No resetting.” You smiled, before making your way through the ruins.

You didn’t know why it felt so eerie. A place that Toriel once held your hand through was now overgrown with weeds, the already cracked walls half falling apart. You thought that maybe it was only Toriel that made it seem like it was a home. You could only dread what the home itself looked like.

Everything was disgustingly quiet. A throbbing, hideous silence hollowed out the love that once filled the rooms. The home was surprisingly dust-free, but considering what dust is to monsters, you were relatively glad.

You wanted some pie. Maybe when you return, you’ll ask. You remember the warmth filling you, and you smiled, fingers ghosting over your stomach. In a strange way, you almost missed the first journey. Everything was frightening, and new. It seemed so sad and despondent. 

But that wasn’t why you were here. You stifled a yawn, and thought, slipping into the bedroom you were brought to, testing the bed with your hands, before plopping yourself down on top of it, your bag hitting the ground with a soft thump. 

For a moment, you stayed like that. Simply on the bed, in the silence. You grabbed for your phone, turning to lay on your back, phone hovering over your face as you brought up Sans’s name, the thread of texts making you smile.

“You really care.” You chuckled, rolling your eyes. He was so sweet. He liked to pretend he was some kind of breezy, collected soul. But he cared more than anyone you had ever met. He told you about the resets. It freaked you out to think you had that kind of power. Even unknowingly, you had caused a reset before. The thought sent a shudder down your spine.

_‘Hey Sans. Just letting you know I’m safe. Ready to explore! :)’_

You sent the text, watching it go through without a problem, relief swelling in your ribs. You would hate to think the service down here was what caused Sans to have a meltdown. 

The phone buzzed unexpectedly in your hand, and you loosened your grip, the phone smacking into your nose and sliding beside your head. For a moment, you laid dazed, before grumbling and snatching the thing back, narrowing your eyes at the screen as if it had personally attacked you.

_‘be safe. undyne’s here. she wants to say hi.’_

You grinned at your phone, as you moved to reply, the phone rang in your hands, and you quickly answered the call, pressing it to your ear.

_“Hey, punk! Papyrus said some thief stole something of yours! I hope you punch ‘em in their stupid face!”_

“Hey, Undyne. I’ll give it my all.” You giggled, listening to Papyrus wailing in the background. It was nice to have some noise for a change. “I was gonna take a nap. I need my energy. Want me to text you when I wake up?”

_“You better! Or I’ll be ramming my spear right in your- Hey, gimme back the phone!”_

_“...goodnight.”_ The voice was lower, definitely Sans, as the beeps sounded from the speaker, you looked at your phone and sighed, opening up your music and putting something on. Soft songs left you feeling comforted enough, setting the phone beside your head as you curled up under the blankets, cursing yourself for not bringing anything to sleep in. For a moment, you were still, before shifting yourself out of your clothes.

“There. Now they won’t be gross. I hope.” You stared at the pile, feeling disturbingly vulnerable. You shuffled further into the covers and let the music lull you to sleep.

You were walking. Everything black. Everything silent, even your footsteps. You heard nothing. You wanted to shout, opening your mouth, it was filled with tendrils, reaching deep into your body, your throat bulging, you began to cry, waiting to die. Something had started to speak, echoing in your head.

You woke, jutting out of bed, crying as you fumbled for your phone, shaken. You looked carefully at it, as your grogginess left you, you sniffed loudly, wiping your eyes. 

Your music had been paused.

Midway through a song, it had been stopped. You shook as you held it, eyes wide, you scrambled to shove your clothes back on, snagging your backpack and throwing it on, before distancing yourself from the home as quickly as possible. Your nightmare felt too real. Your fingers stroked your neck, swallowing. You didn’t want to sleep ever again.

You were snowed on. You had forgotten the snow, squinting as flakes pricked your skin, dousing you in frigidness. You shivered and breathed, thick plumes of air steaming from your mouth as you trudged forward.

The bridge. You looked up at it. It was comical, now. The bars were hilariously big. This was where you had met Sans. The stupid whoopee cushion brought a smile to your face. He was so friendly to you, and you even enjoyed Papyrus’s puzzles. _Shit._

You took your phone out and frantically typed, just to let everyone know you were on the move, sliding your phone back. You were hit with the memory of the home, your music had been stopped somehow. 

It was barren. Snowdin was bare, and even the shops were abandoned. Not a trace of life. Not even an insect. Everything was starting to eek you out too much. You gathered your thoughts at the large tree in the middle, stroking the peeling bark. 

You had travelled up from Snowdin, establishing your bearings. When you saw them.

The boat. The cloaked figure hummed that same tune from before. You remembered the low gurgle. You nearly tripped running up to them, breathless and in a state of disbelief, the shadowy face turned to you.

“Tra la la. Care for a ride?”

“Y-You! You’re the River Person! You told me about the man with the hands years ago!” You rambled loudly, as the River Person hummed to themselves.

“Care for a ride?” They asked again, and you bit your lip to the point that the skin started to break, nodding to them.

“Where would you like to go?”

“...Um...W-Waterfall.”

You were a little unsure of the names. King Asgore was awful at it, so it helped to make them glaringly obvious. Still, you hoped that it was correct. Seemingly so, as the River Person pushed off.

You listened to them hum delicately for minutes. Until the gurgling stopped.

“Tra la la. Beware of the man who came from the other world.”

“...W-Wait, what?! No, please! You have to tell me! Do you know who Gaster is?!” You grew frantic. The River Person either could not hear you, or chose to ignore you, steering the thin boat down the stream. You could _cry_ at the frustration. “Why won’t you talk to me?!”

You docked, and the River Person turned to watch you step off from the boat.

“Come back again sometime.”

“Please tell me what you’re talking about. Do you know him? Do you know Gaster?” You tried again, as the River Person fell silent. 

“...Beware of the man who speaks in hands.”

The phrase sent your head reeling. The same phrase. It was haunting you. 

“I-Is that about him? About Gaster?”

“...Care for a ride?”

The conversation had gone cold instantly. You tried to smile, weak and half-hearted, before you waved goodbye, seeing the shop the old turtle used to keep at. Unsurprisingly, he wasn’t there. You knew they were all on the surface. And yet, it managed to feel as if everyone had died. 

You wandered around aimlessly for what felt like a lifetime. You had rooted around in your bag for food, eating as you walked, before something small caught your eye.

A child…?

“Excuse me?” You called out nervously. You could feel the throb in your stomach tighten. The small monster seemed to not hear you. You drew closer, enough to stand beside them, crouching. When they turned towards you, you jolted back, nearly losing your balance. White, pupiless eyes stared blankly at you, their flesh grey and seemingly frozen into place. They looked familiar somehow.

“Have you ever thought about a world where everything is exactly the same...only you don’t exist? Everything functions perfectly fine without you. Ha...the thought terrifies me.”

The voice was a raking inside of your head. As if you shouldn’t be talking to it. A high pitched and yet somehow jarringly low mess inside of your brain. The child looked utterly dead, and your heart hitched in your throat.

“A-Are...are you okay?” You managed to voice, dazed and confused. The child stared unblinking at you for a moment longer, before looking out at the inky depths of the water below.

“...Please, forget about me.”

The words were barely heard, before you felt a ringing in your ears, screwing your eyes shut as you backed away from the child, once the noise had calmed, you slowly allowed your eyelids to open, to find nothing.

You couldn’t even remember what had happened. Only the dull ache in your head. You stumbled around in a disoriented mess, until you had found your way into Napstablook’s house, curling up with your bag on the floor, simply wanting to sleep the feeling away.

**Notes for the Chapter:**

> I'm really into this story! I just wanna get it all out there! Are you spooked yet?


	4. A Glimpse

You felt cramped. Your body against the hardwood flooring, curled up and clutching your bag. 

You sat up, grimacing. You didn’t know why you just had to sleep on the floor so badly. You had a perfectly good sleeping kit in the backpack. It was a baffling decision. It took you a moment to realise you had yet to text your friends, patting your pockets until you found your phone. 

It had been three days.

“Y...You’re kidding...that can’t be right…” You whispered to yourself. Missed calls and messages filled your screen up, and a sinking feeling hits your chest like a brick house. The wind is knocked from your lungs as you scramble to call Sans, who picked up on the first ring.

_“are you okay?”_ He sounded tense. You were used to seeing him trying not to worry. Hearing the raw ache in his voice hurt your heart.

“Yeah. Sans, there’s something weird going on here. I went to sleep three days ago. And before that, I had some kind of nightmare- I found the River Person, Sans. He said the phrase. ‘Beware the man who speaks in hands.’ He didn’t offer me anything else. Something’s not right down here any more.” You struggled to speak clearly, babbling in and out of thought, trying to shove your ideas out before you forgot them. There was something you were missing, but you didn’t want to waste time figuring it out.

_“...this sounds real bad, you know. maybe you should come back, now.”_

Sans was clutching the phone with so much force, he almost worried he was about to snap it in half. He hated worrying. He hated the feeling in his soul he got when someone he cared about was in trouble. The constant resets had told him to abandon the feeling. But there were no more resets, now. You were in danger of disappearing, and nothing could bring you back from that.

You swallowed, silent as you stood, your aching legs strained under the feeling. Sans could hear you breathe deeply.

“I...I have to just get a little further. Just a bit more.”

_“and if you don’t find anything?”_

“...Then I’ll just go home and pretend this didn’t happen.” You had to admit, sighing. But you were going to. You had to. Something wasn’t right in here. You had offered Sans a small goodbye, hanging up, you fished around your bag and pulled out the charger, pushing it into the slot and leaning against the nearest wall.

All this for a dead man. You had waltzed into the abandoned home of monsters in search of a rumour for the sake of your own stupid curiosity. The thought made your eyes prick with tears.   
You forced yourself to eat. Your body needed it, even if you had no appetite for anything. You could hardly believe this was the same place. As a teenager, this area was an eerie wonder, with echoing flowers and enchanted monsters. The same flowers were wilted and ugly, there were no monsters to be enchanted with the rocks on the ceiling. They had the real thing, now. Thanks to you. You felt your pride buzz as you managed a smile to yourself.

Something was still about the area. The rush of water no longer rang out in the cavern. Nothing did. You blinked, pulling out your phone, checking the time. You flicked the phone unlocked and pressed onto the clock icon. Only to have it crash and exit. An arched brow, you attempted again, only to get the same response. You had gone for a third time, until your phone had shut off completely. Panic overwhelmed you and you shook the thing, desperate for a response.

“No, no, no! Oh _fuck_ , this is so bad. Oh no, please don’t do this.” You lightly hit the phone, until you shoved it roughly into your pocket, furious. 

You began to walk. There was nothing else for you to do. Just walk. It was almost like taking a nostalgic tour through the Underground. You were nearly enchanted by the soft glow of the crystals, until a white noise-esque babble began to grow in your head. You cringed at the loud static sound. It grew when you walked forward, growing and growing, until your head throbbed in pain, teeth gritting as you tried to battle it out.

All at once, it stopped.

Your eyes flew open wide, looking around, before you noticed the white door. It looked out of place, its clinical sleekness bothered you. A door built into a cave wall. It wasn’t right. You reached to touch it, surprised to find it solid, your heart was leaping out of your ribcage in fear, as fingers tested the strength of the door, you dropped your hand to the handle, gripping it too tightly in your palm.

You swung it open.

It was a blinding white room. As soon as you stumbled in, the door shut immediately, and your heart stopped, wide eyes fixated on the figure in the room with you.

It did nothing. Hollow, cracked sockets remained lifeless, the head carried black breaks in the whiteness, and you winced at the implication that the thing’s skull had been broken.

You were too fearful to approach, your back against the door, you kept your distance. You tried to reopen the thing, jiggling the handle as your gaze stuck onto the figure. You were intensely staring at its face, until your sight faltered and you looked down. Half hidden hands loosely gripping the edges of its coat, holes where the palms should be. 

You didn’t even have enough time to scream, one blink, and the creature was inches from you. It towered, once void-filled sockets burned with a strange magic, the soft smile looked down on you, and you finally tore a scream from your throat, startling the thing enough for you to lash out in fright, your back slamming against the door. 

“P-Please don’t hurt me- I can’t get out-” You choked out brokenly, the creature looked at you strangely, mouth opening, it started to laugh. A dark, ringing sound in your mind.

“... _You_ are the...anomaly. Very, very...interesting.” It spoke. A vile, twitching echo premeditated the words before his mouth shifted. You trembled, before capturing a glimpse behind the tall monster.

Two large hands, exactly the same as its own, with holes in the centre, skeletal fingers outstretched as if to embrace.

“...You’re _him_. You’re Gaster.” You whispered. His smile twitched, and he chuckled softly.

“You are...correct. A clever anomaly.” 

You had done it.

You couldn’t move, pinned to the spot, but not by him. Questions flooded you, too many, your head spun as your legs buckled, your vision blacking as the last image you managed to see was _him_. 

“...-man...up!” 

You could feel your head moving. Noises swam in your body and you tried to mimic them, your mouth opened, you could feel yourself cough, your entire body twinging in pain.

“...-ing to be okay?”

It was familiar. Papyrus? Your eyes fought to open, the harsh light flooded into your pupils and you groaned pitifully, before trying to shrink away from the feeling.

“Human! You’re okay!” Papyrus’s voice rung clearer, and you furrowed your brows, huffing a short breath. Your body felt as if it were on fire. The skeleton’s hand was firmly against your head, fingering through your hair to soothe you. It was a kind gesture.

“W-Where am I…?” Your voice croaked in your throat, slowly you were sat up by Papyrus, and your eyes finally adjusted. Sans, Undyne and even Alphys had been around you. Relief washed over their faces. “...How did I get here?”

“W-We don’t know.” Alphys was the first to answer, fidgeting with her lab coat. She must have been in some kind of a meeting. For some reason, you found it funny, chuckling to yourself, your head spinning. 

“I-I did it. I met him. Sans...I met him.” You turned your gaze to the skeleton, whose sockets were nearly pitch black, the tiniest of pinpricks stared back at you. He barely believed you. 

All you wanted to do was sleep. You had dozed off easily. You stirred in the middle of the night, vision hazy, you looked around. This was your apartment. You were on the couch, everything was in its usual place. But you couldn’t have gotten here without your keys. You looked around, patting your pockets, the couch, leaning stupidly to scan underneath the sofa, tipping and landing awkwardly onto the floor with a pained grunt.

You had trudged into the kitchen and downed four cups of water, before raiding the fridge and effectively inhaling whatever food you could. You felt _starved_. You were just refilling your fifth cup underneath the kitchen tap, when a shadow caught your eye, and you jolted, spilling it over yourself.

“ _water_ you doing up?” 

“ _Sans_. You scared me! Why are you still here?” You protested, and he laughed kindly, shrugging and offering you a casual wink.

“i guess i’m just _bone_ to be scary, huh? i wanted to make sure you didn’t have to wake up alone.” Another wink, and you relented, laughing at the stupid joke. They restored your normality. You lowered the cup in your hand to the counter, and paused.

“...I saw him. Gaster. He _talked_ to me. He was all cracked and...broken looking. And he had these big hands floating behind him, with holes in his palms. He said I was...something. An anomaly? He laughed…” You trailed off. The memories were strangely blurred, his eyes seemed to vanish, only managing to recall the cracked skull and his hands. Everything else had burned away. You cursed yourself. 

“how’d you get back into your apartment?”

“You mean, you didn’t get me in here?”

“you’re the only person with the keys, right?” For a moment, both of you were silent. You could feel a stiffness running through your bones.

“That aside, how did you find me in here?”

“i was gonna walk past your apartment. wanted to see somethin’,” He vaguely avoided telling you, and despite your curiosity, you let him continue. “your door was cracked open. i thought someone had broken in.”

“My door was...open? But my keys were in my bag. Oh, _shit_. Where’s my bag?”

“don’t worry, it’s here. everything’s here. i know, it’s not makin’ sense to me, either.” Sans admitted with a soft sigh. You slowly wandered over to him, wrapping your arms around him tightly. It was utter relief to see familiarity. In such emptiness, to feel his fingers on your back, you sighed into the embrace, smiling.

“...I have to go back. And find him. He’s _alive_! I have so much to ask him.” You pulled away, barely noticing the soft glow in Sans’s eyes, before he twitched.

“don’t go alone, if you’re going back.”

“I’m not bringing any of you. You’ll get hurt.”

“i’d rather me get hurt than you.” Sans crossed his bony arms, shooting you a look. You stilled, frowning sadly.

“There was a door in Waterfall. A door. In the middle of the wall. He was in there. But, when I went to look at my phone nearby, it broke. It just turned off. And the white noise…” You changed the topic, the memory started to burn into you, and Sans’s pupils glanced at your face, looking for any emotional trauma.

“i don’t think you should go back.” Sans confessed sadly. You slowly wandered out of the kitchen, silently allowing him to follow you, until you were both on the couch. You brought your legs up to sit on top of them, picking at your shirt. You felt gross. You wanted a shower.

“...I have to find out, right? The River Person warned me about him for some reason-”

“he’s _dangerous_.”

“They didn’t tell me everything,” You ignored him, to his displeasure. “I barely know a thing, even though I saw him. It feels like a dream, somehow. But I really did it. Why was I warned, Sans? Gaster must have wanted something from me all those years ago. I sound really obnoxious.” You laughed, easing the tension from yourself. You felt ridiculous for putting yourself on such a pedestal.

“whatever he wanted, he might still want. you could end up in a lot more than you want.” Sans warned, though his tone was light, you knew he conveyed more threat than he let on.

“Do you think he’s mad that I broke the barrier? Everything around him is a mystery. I have to figure it out. What if he comes here to hurt someone I care about?” The thought had never occurred to you before. If Gaster had dropped you off here, then he was free to move anywhere. The idea of him delivering some kind of vile torture on one of your friends to draw you to him sickened you. “I can’t let him. I think...even if I wanted to back out, isn’t it too late?”

“what do you mean?”

“Nothing’s stopping him from coming here. To me. If I went back and saw him there...I’d be putting way less people at risk.”

“you have to start thinking of yourself as a person, y’know. you matter just as much.”

For a moment, you blushed. The sincerity in the skeleton’s voice had you smiling, and you giggled.

“...Thanks, Sans. That was very nice of you.”

“what can i say? i really put my _heart_ into it.” He laughed when you did, stifling the desire to roll your eyes at such a lame excuse for a pun. But truthfully, it was a good distraction. 

“I’ll be more prepared. I know what I’m looking for. I can’t just leave it now. I mean...what if he’s trapped?”

“maybe it’s for a good reason.” Sans argued, and you frowned at him.

“Well, there’s only gonna be one way to find out. I’ll take a couple days, and then set out again. I can’t guarantee that my phone’ll work. Last time he wrecked it for me. Speaking of which, where is it?”

“i put it on your bed. it works fine.” Sans reassured you.

“Glad to know he didn’t outright break it.” You sighed, uttering a breathy laugh, slouching back into the couch. “...He was a skeleton, you know. Or is, maybe. He had bones. He spoke like his own body was echoing it. I can’t explain it well. I’m gonna find out what he wants from me.”

“...i think you’re gonna have a bad-”

“Nope, I won’t hear it. You can argue all you like, but I’ve made up my mind. I want you and the others to be safe. You won’t be very safe if some corpsy scientist dangles over your bed while you sleep, will you? No, you won’t. Meeting him far away is the best option I’ve got. There’s no way I’m attempting to bring him to my apartment.” You shrugged, as if your logic was faultless. To you, it was.

The days passed, and you slept fitfully. Dreams of hands, of haunting, robotic speech. Hands gripped and pulled until you popped and fell apart, and that hollow grin watched you without mercy. It was the same dream, for three nights in a row. You woke with your hand clutching your chest, your anxiety wracking your body until you calmed down. 

Today. 

You would have to find him today.

**Notes for the Chapter:**

> Finally, right? Was he spooky enough? Does he make your heart flutter?


	5. Gripping

**Notes for the Chapter:**

> Aah! I just wanted to say a huge thank you for the support! I wasn't expecting nearly as much as I have, and I'm super grateful! It's really encouraging to see!

Sans had watched you pack. You were stuffing clothes into your bag and cramming in more food. The sleeping bag was a pointless endeavour, considering the amount of spaces you could sleep (including the floor, you think, sighing to yourself).

“why are you so interested in him?”

“I just want to know why I was warned.”

You paused, to watch the clock on the wall. It ticked by casually. Something in you begged to not return. You had a bad feeling, you were warned for a reason. _Don’t go back_.

“you look like you need a _time_ out.” Sans joked, noticing your absentminded staring, urging you to sit on the edge of your bed. You complied, simply because you felt too drained to argue. 

“You’re right, you know. It’s a bad idea. I went there with the determination that I’d find him and ask him about everything that’s been bothering me about him. But when I actually saw him? It was like...staring up at a terrifying nothingness. I couldn’t even speak. I was sure he was about to kill me. But ever since, I keep having nightmares. Do you think...he’s causing them?”

You had rambled, and Sans drank in your words and mulled them over in his head, pupils cast at your leg, which had started to bounce. He said nothing to you for a while, and though his smile was never gone, you could tell it was an effort to keep it up. 

“listen, i know i can’t stop you, kid. the nightmares might be him, or might be you stressin’ out about it. and i’ve said this before, but...it’s not worth going.”

“...Yeah. Yeah.” You could feel your heart sink. Sans was right. You were overreacting. Whatever had happened down there deserved to stay down there. You still felt as if you had forgotten something important, but perhaps now it was never going to be worth remembering. “The River Person’s still down there. I wonder why.”

“maybe they just like it better. _boat_ i could be wrong.” He shrugged, smirking. You cringed, laughing. 

“That might be the worst one, yet. Hey, isn’t Papyrus supposed to be cooking tonight?”

“yeah. i gotta make sure the house doesn’t fall apart. you know how undyne is.” You both share a chuckle, before he sets about leaving, lingering for a moment by the doorway, gazing at you. “you gonna be alright on your own?”

“I’ll be okay. I’ll probably finish off some work. Which is...grossly overdue.” You winced, and Sans grinned, a genuine smile, which ebbed your nerves. Truthfully, you never wanted to be alone again. But you were within the familiarity of your own apartment. Everything would be fine.

“see you around, kid. i’ll text you to keep you company.”

You nodded, grinning, watching the skeleton saunter down the hallway. You pushed the door closed, and leant on it for a moment, worrying at your lip. 

You were quick to turn the television on, settling on some reality show, hugging a couch pillow as you curled up beside the arm. The women on the show were fighting about something, you uttered a soft laugh as you slid your eyes closed, hoping to at least doze off.

You woke up, after having an uneventful sleep, did your paperwork and sent it, returning from the lobby of the complex to your apartment, looking it over. The fact that you hadn’t had a nightmare bode well for you.

“I should tell Alphys about Gaster.” You mused to yourself. After locating your phone, you looked it over, unlocking the screen and bringing up the thread. You asked to meet for a chat at the cafe again. It was a nice place for idle talk. Maybe Alphys didn’t want to talk about Gaster. The thoughts in your mind changed quickly, and you felt a knot in your stomach. 

Your phone buzzed, and you smiled at the agreement. But you decided that you wouldn’t bother mentioning it. It was better left forgotten. Everything was.

It had been two months.

You had settled into your life once more, and though the thoughts still plagued you, you pushed them away. The nightmares had stopped so quickly. It must have been you causing them. You laughed to yourself in the shower at the thought that Gaster was the one behind it. The only thing that still bothered you was how you ended up back in your house.

“It had to be him.” 

You didn’t want to think about it. The shower was warm, you let it drain your thoughts away, eventually stepping out and shivering. You hadn’t realised how much you took your shower for granted, thinking back to the Underground, cringing.

You had towelled off, choosing a baggy shirt and some panties at random, fiddling idly with the small buttons on the front of the underwear. You pondered buying new clothes to sleep in. But it seemed pointless to make the effort to look good to bed unless you were bringing someone home. And let’s face it, you weren’t.

You had closed the door to your bedroom, drinking in the accustomed surroundings. The warm smell of laundry broke out a smile on your lips, the pile on the bed remained unmoved since this morning.

You took a step, and everything felt cold. 

Your head spun strangely, vision blurring as your back hit the wall beside the door. You were pinned, pulled, you felt the air leave your lungs as you tried to shriek in pain, your spine pressed flush against the concrete, until your closed eyes opened.

You were in nothingness. For what seemed like an eternity, you were in a void. You opened your mouth to speak, but nothing came. You could feel the vibrations against your throat, the breathlessness in your chest, but no sound rung from your lips, and your eyes pulsated at the inky blackness, frantic to find any sort of light.

You slammed your back against something warm and solid, screwing your eyes shut as the sudden light ripped into your pupils. The air was humid, and you lay still for a moment, gulping in the warmth before attempting to open your eyes again.

“This...this is the Underground.” 

You looked down at yourself numbly, still in an oversized shirt, fingers grazed along your hair, feeling the remaining dampness tangled in the strands from your shower. Everything ran desperate in your mind, you stumbled to stand, legs almost giving straight back out.

“But I was home. I-I was going to bed. This isn’t right.”

A barren, red landscape stretched in front of you. You turned to look around, spotting Alphys’s old lab, before reality started to dawn on you. You were in Hotland. You had gone into your room, and something pushed you. The burning in your back. You trembled, clutching your sides, as if you were going to vomit, your head spinning.

You shambled your way down, and was met with the soft rush of water. The River Person turned to see you, humming. You began to cry, stumbling towards them on unsteady legs.

“Tra la la, would you-”

“Y-You have to help me. I was dragged here. You know who I am, don’t you? Did Gaster drag me here?” You sniffed, hot tears dripping from your jaw. For a moment, you thought you could see the River Person give pause.

“...Would you care for a ride?”

“You...y-you don’t even care, do you? You don’t understand, I was _taken_ from my room above ground. I don’t know if you can help, but could you at least tell me how that could have happened? I know you know something about Gaster!” You raised your voice, as the cloaked figure stared absentmindedly back at your shaking figure.

“...Sorry.”

It was the first time the monster had not been cryptic. The word jarred you entirely, and without warning, they pushed off from the dock, leaving you. You opened your mouth to yell, to call out, to do _anything_. 

_Sorry_. The word tore into your soul, and you tensed, before slowly returning to the same place you had been dropped. 

As per usual, everything was deserted. There was a silence that rattled your nerves, now with the knowledge that you had forcibly been put here. You didn’t want to go into the lab. You would save it, leave it alone. You wandered, fingers pulling the end of your shirt, feeling it ghost along your thighs. 

A large monster caught you off guard. It was just a head, mouth gaping, eye vacantly staring. Even as you approached, it made no intention of moving. You cleared your throat, but upon seeing no response, decided it was perhaps easier to simply speak.

“D-Do you...hello? Are you okay?” You bit your lip. You could feel the dryness of the skin, picking at it with your teeth in anxiety, as the monster inhaled.

“I understand why Asgore waited so long to hire a new Royal Scientist.” The thing spoke, and you winced. It was a strange static sound, the words it spoke were barely audible over the thick haze of white noise.

“W-Why?” You asked, bracing yourself. The monster took another short inhale.

“The previous one, Dr. Gaster...his brilliance was irreplaceable,” The monster wheezed a strange laugh, which hurt your ears. “However, his life...was cut short.”

That was the rumour. You allowed yourself the luxury of sitting down, your legs feeling useless as you attempted to fight the headache creeping along your skull.

“One day, his experiments went wrong, and…” The monster paused. The silence felt uncomfortable, you twitched and fidgeted as the monster’s eye remained unblinking, even in the heat. “Well, I needn’t gossip. After all, it’s rude to talk about someone who’s listening.”

Your eyes widened, scrambling back up onto your legs, you swung round and stared at the edges of the road, the darkness providing you nothing. You had turned to ask what the monster meant, but started when you were met with nullity. 

You reached your fingers out to the space where the monster had been. You had so hoped to touch something. To find some solidity. You held back tears as you found emptiness. 

There was nothing else. You were too tired, too confused. Gaster had brought you here. But he had left you. You couldn’t begin to know why. You ambled back down to the start of your travel, eyeing up the lab fearfully. 

You hated the place. Ever since discovering the true lab hiding underneath. The Amalgamates, the dripping mass of bodies burbling pathetically at you, had shaken you to the core. You were disgusted with Alphys when you found out. She explained, but the terror in your heart had taken months to even begin wearing off. The lab was nothing but grim memories.

The door still worked, whirring open as you drew close, and you swallowed thickly, your bare feet touching cold tile, softly whining at the feeling. It felt much colder in here, than in the rest of the Hotland. One side of you told you to be grateful, as the other erupted your flesh into goosebumps, the stark contrast in temperature had you shivering quickly, and you pulled on your shirt, hoping for a sense of protection.

You wished you had your phone. Or anything. Your back ached, your legs felt strangely unsturdy as you quietly stepped along the clinical flooring. All of the anime merchandise had gone. There was no power, oddly. The door worked fine, but the rest of the lab was deathly quiet. You made your way up to the second floor, searching for any sort of leftover paraphernalia. You were greeted with a hollowed out office, the bookshelves, table, walls, all laid bare before you. You didn’t know why it bothered you to have it so desolate.

It was all your fault. 

You were here because you had been so intent on finding a rumour. You despised yourself for being so clueless. As you approached the opposite door to the exit, you found yourself pushing against it, grunting softly as it remained fixed shut. 

“Why won’t _you_ open, but your buddy will?!” You seethed, slamming your shoulder into the metal, only succeeding in a rippling pain buzzing in your muscles. “Fine. I’ll go out and around. For fuck sake.” 

You cursed, only just noticing the faint echo against the steel walls. You felt a strange sickness overcome you, recalling the way Gaster spoke. Like a reverse echo. The words came from the air before his mouth had even opened to speak. You were lost in thought, trying to rationalise yourself, before you had bumped into the lab door.

“Hey- what?!” You pressed a hand to the entrance door. It refused to move. You pressed harder, wiedling the same results. “But I got in through here. It was working fine before! F-Fuck! Don’t do this!” You shoved your weight against the door, hearing a groan of metal creaking against itself, but nothing opened. You were trapped in here.

You slid to the floor, tiles touching your bare thighs as you lightly hit your head, lolling it back to bump against the metal behind you.

“Please let me out…” You whispered. You despaired. You had lost the will to fight against the metal. Questions screamed at you, but you knew _nothing_. You didn’t want to cry again, rubbing your eyes as you brought your knees to your chest, hugging your legs tightly, learning your forehead on the patella.

Sans was right. You didn’t want it. You were in too deep, and though something told you to continue deeper, most of you wanted everything to go back to normal again. 

You wanted the excitement again. Years had passed, the barrier broken, your life had returned to that of an average person. Discovering the cryptic note had given you the revelation that you could adventure. You should have listened to the damn skeleton. You should have _listened_.

“I’m so stupid.” You breathed, sitting in the silence. You felt an ugly draft crawl across your exposed legs, glancing across the dark lab floor, biting your lip painfully hard.

The entrance to the true lab was there. Probably open. Your throat tightened at the thought, gazing at the murky darkness. You didn’t want to move. You wanted to wait until you either died or the door opened. 

You closed your eyes, and hummed. Softly, you let the echoes ring in your ears, the only comfort you could offer yourself. Something touched your ankle, your eyes flew open, and you were yanked from the door, your head smacking on tile, you began to shriek, the skeletal hand gripped tighter.

You were sliding along the floor, lashing out as your hands tried to clutch onto the small dips between each tile, your fingernails throbbing as the pressure ripped you from your grip each time. Your shrieking echoed throughout the entire lab, you begged to be let go, but the hand did not stop to listen. 

As you were pulled, you noticed. The true lab entrance. You screamed louder, eyes fixated on the door ahead. 

“Even after all my prompting, you remain...reluctant.”

The echoing. The words spoken before the actual voice. 

_Gaster_.

You tried to kick, your hands clutching the doorway, your fingers cracked as you were forced ever further down into the depths of the forgotten laboratory. The voice gave a huff of a laugh.

“...Determined.”

**Notes for the Chapter:**

> Now the fun can REALLY begin, huh?


	6. Snatched

You should have fallen. 

The first time you had gone into the true lab, the elevator had snapped and crashed to the ground. You remembered the way your body lurched and your legs buckled under the feeling. 

But you were held. You could see nothing in the darkness, any hopes of looking around in search of what was keeping you secured was futile. The hand around your ankle had disappeared, and you jolted when the soles of your feet touched frigid ground. 

“You must forgive me for my forwardness, human.”

You flinched at the darkness, the soft whirring of machines around you felt too loud due to your heightened senses, the fear pulsing through you. There was a soft clank, and the room lit up dimly. You squinted, not trusting your environment enough to close them fully, forcing yourself to adjust. The voice had been quiet. Perhaps waiting for a reply or an acknowledgement.

“A-Are you Gaster?”

“You have mentioned me before, I believe. I had confirmed your suspicions. I am indeed him.” The echoing voice felt so much louder. You looked towards the source, all fear in you was met with unbridled horror. 

Gaster towered as he had in the room you had first seen him in. Only closer, standing straight with his hands clasped behind his back. The cracks on his skull dipped inside of his head, his sockets watched you intently, two different sized balls of light focused on you. 

“You brought me here, didn’t you? _Why_?” You tried to step back, grunting softly as you were pushed forward. Glancing behind you, a hand lingered, large and waiting patiently, the hole in the middle obscenely exposed. You turned back to Gaster, who was smiling politely.

“Ah, well, yes. I did bring you. As I am sure you are aware, you are rather special. The fact that you had found me at all in that room suggests as much,” He took a step forward, shoes clicked on the cracked tiles, you stiffened, and he stilled immediately. “You have nothing to fear from me.”

“Y-You ripped me out of my room and put me here! You’re not even supposed to exist! You’re supposed to be _dead_ -!” You had caught yourself too late, as Gaster’s pupils dimmed in their brightness, he chuckled almost sadly, the reverberating noise bouncing off of the old lab walls.

“I never tried to convince you I was alive. I am...neither, theoretically speaking. I believe you humans had a theory regarding that. Something about a cat…? Ah, well. Nevermind. Truthfully, I had expected you to return here of your own volition. Upon waiting, I realised that perhaps it was not to be the case.” He sighed, and for once, his smile faltered. You didn’t know he was capable. 

The rumours existed for a reason, then. You pondered, trying to ease yourself into the situation, still half pressing against the hand whenever you felt frightened, as it urged you forward once more. Gaster had thought it out too quickly, blocking you off from an escape. You felt like trapped rat.

“So you...just _took_ me? How did you even do that…? Were you the one that brought me back to my room when I first saw you?” Your mind started to scream with questions, you steeled yourself with determination to try and unravel the mystery. Gaster’s pupils flickered as he watched you.

“I do not exist to regular boundaries. And I am, indeed. Though by the use of magic, and not my own physical body. The same one that...well, took you. I once again express my sincerest apologies for any discomfort I may have caused, however you were not cooperating like I had envisioned.” He almost looked irritated with you, for a split second, before the silence took over you both. 

You had managed to calm down, just slightly, staring up at the skeletal monster. You had to remember every detail. His old black coat, the collar neatly arranged by his cervical vertebrae. He looked almost _kind_. But you knew better. No kind soul would be this way.

“So those rumours...an experiment went wrong? You scattered, and now you’re...whatever you’d call this?” You hadn’t considered how insensitive that may sound, wincing slowly. Gaster offered you a quiet chuckle.

“You could perhaps say that, yes. Ah, please, won’t you sit down for a moment?” Gaster had silently taken a step, hoping for you to follow in his movements. You remained still, and he sighed, returning to his original standing. “Or, perhaps not. Are you not comfortable?”

“I hope you’re kidding.” You shot back, angry that he’d even consider asking. He looked genuinely upset by your reaction, his hands unclasped from behind him to dust his coat, and you narrowed your eyes, watching bony fingers flick at the fabric. 

“I understand your frustration. I have apologised, and I cannot offer you much more.”

“You can take me back home.” You deadpanned, irritated. Gaster shifted, as the hand behind you tensed visibly, fingers growing rigid, as if he was anxious about you trying to run.

“...I cannot. Not yet. I have just gotten you here. I have a number of experiments-” 

“ _Experiments_?” You echoed, feeling your heart throb in your stomach. Gaster’s eyes flickered in realisation, and he promptly clasped his hands behind his back again.

“Nothing that will cause you any amount of harm or stress, I assure you. I wish to study you, simply. I have never seen a living human before, let alone one with enough determination to destroy the barrier.” He smiled fondly, he genuinely looked excited, like a child with a new toy, taking a careful step closer, you tensed, but he no longer moved back, staying in place.

“A living human? And you know about the...no, that’s a stupid question.”

“No question is stupid, human,” He was quick to reply, and you blinked, laughing nervously. “And you must know of King Asgore’s collected souls…? From the dead children prior to your visit? When I had seen them, they were bodies.” Annoying to experiment on to say the least, but Gaster was much less keen to divulge such information to you, seeing the trepidation in your studying gaze.

“Oh. Right.” You didn’t want to remember. Yet another monster that Sans had little intention of forgiving so quickly. You didn’t know such a carefree skeleton could hold such a grudge. Though you didn’t have it in you to blame him. “I want to ask something.”

For the first time, you weren’t afraid. Constant exposure to Gaster, to the situation, had made you comfortably numb. If anything, you were tired. You had been walking, crying, in a near constant panic. You stifled a yawn at the idea, and Gaster picked up quickly, though made no reference to it.

“You may ask.”

“When I first came down here...when I was a teenager? The River Person warned me about you. Why? And who was that grey person who said you were listening?”

You had felt the pressure on your back, jolting as the hand urged you forward, Gaster took small steps away, and prompted you to follow of your own will, silently pleased to hear the soft pat of your bare feet lingering behind him. 

You sat on a bed. There were rows of them, in the dim light you could make out the silhouettes of frames. Gaster contemplated sitting beside you, but perhaps it would be too close. Instead, he seemed to crouch, his coat pooling around his body as he smiled. You felt like a child.

“Despite my knowledge of a great many things, I could not answer you. While it is true I had been… _observing_ your actions, I made no move to harm you,” Gaster brought a finger to his jaw, stroking along it as he thought. The River Person had warned you, but Gaster could not think as to why. He would ponder upon it later. “And that monster is almost the same as I. They were a sort of memory, not technically existing. Think of it as a flashback that managed to exist in the same timeline as you.” 

You couldn’t wrap your head around it. You knew about time jumping, as explained by Sans many years ago, even Flowey had proven the possibility of doing such a thing. But to explicitly talk to something that existed in a separate time to you just hurt your head to think about.

“...Observing?” You returned your thoughts to the conversation, and Gaster’s pupils brightened nervously.

“In a scientific sense. You defied normality with your ability to shift and repeat time. You, with your determination alone, managed to break down a barrier meant to keep all monsters inside. Understand that I have not seen such a thing in any monster. I cannot say if other humans have the same ability, but I know you do. I’ve seen it. You are an _anomaly_.”

You fiddled with the bed sheets under you. The tension swelled in your chest as you thought the words through. You didn’t want to think you were an outlier, and that you were special, instead of a statistic. But to a scientist, perhaps he never intended to see you as an individual. 

“You...called me that before, didn’t you,” You didn’t ask, the utterance more like a muttering to yourself than to Gaster, who gazed at your fingers as they curled and uncurled. “An anomaly. But there can’t be anything else you want from me. I need you to take me home.”

The only way out was through him. He opened his mouth to speak, before slowly closing it again. The hand from before shifted its fingers slightly.

“You...don’t understand. I need to know more about you. About your determination, your abilities, about human understanding in general. I cannot simply let you leave.” 

“So you want to keep me in here like I’m some kind of pet?” You sneered, standing from the bed. Gaster took a shy step back. Despite how much taller he was compared to you, he seemed hesitant to intimidate you.

“Not a pet. I just have to run a few tests.”

“And how long will that take?” You crossed your arms, feeling much colder than before. Gaster cast his gaze down to the ground, knowing you would not like the answer he was about to give you.

“...I cannot say.”

You fell quiet, staring at him. All prior fear had trickled into you at the realisation you may be kept in this lab for the rest of your life. Panic overrode logic as you bolted away from Gaster, catching a quick glimpse of the surprise on his face as you shoved yourself through the hole in the hand, hitting the floor before your legs sprung you up.

You had found the elevator that took you down the first time, trying to scramble up the wall before a hand snatched you. Thick bones coiled around your waist and legs, holding you in place as you screamed, pushing furiously against the fingers.

“L-Let me _go_! You can’t just keep me here!” You shrieked, furious. Gaster had blinked into the room, a wave of white noise flooding your ears, before he watched you sadly.

“I will not be able to let you leave. Please, do forgive me.”

You were frightened of him. You knew he wasn’t kind. You knew. You screamed and yelled, as Gaster kept you squeezed against a summoned hand much larger than your own body, you were shifted to be pinched between a finger and a thumb. You expected to be crushed, to be squeezed to death, but the feeling didn’t hurt. You seethed at Gaster, who remained silent.

“Fuck you.”

“Ah...I am sorry for upsetting you so deeply. But the faster you comply, the faster my tests will get done, no?”

“Don’t talk to me.” You could feel yourself grow exhausted, the adrenaline slowly leaking out of you as tired eyes watched the former scientist. 

He truly didn’t know whether or not to continue talking. He had caused you enough discomfort, he thought. Silently, you were taken to the same bed you had run from, laid down and pinned by a finger pressing into your torso, as a smaller hand forced your arm up, a strong chain clinking as your wrist was cuffed.

“...’Not a pet’. Yeah, sure.” You muttered darkly to yourself. Gaster looked upset, the hands vanished, and he let the silence wash over you both.

“...Rest well.”

**Notes for the Chapter:**

> Gaster seems kind of nice, until you try to leave...
> 
> Ah, how mean.


	7. Split Second Settling

You had fallen asleep. Gaster had been extremely careful to not wake you, lingering over your sleeping form to take notes. He hoped you wouldn’t wake to find him looming around you. A small pair of disembodied hands scribbled notes as he watched, occasionally glancing over them to make sure it read correctly.

“Subject’s chest rises and falls in a specific rhythm...seconds apart. There is an occurrence in which subject will twitch or spasm. This is entirely at random. Subject may also release vocalisations which are also random.” _Strange_. You were an entirely new world.

He could have taken anyone. Once the barrier had been destroyed, a plethora of humans were swarming the Underground. Gaster could have had any one of them, truthfully. But you were different. Your determination was something that he had not seen in any other human before. You destroyed the barrier, you _found_ him. You were strong, and he admired you for that.

He had left you in the room, safe in the knowledge that you could remain sleeping. Perhaps you would settle better with creature comforts. Gaster’s pupils flickered slowly in thought before sighing, resigning himself to a lab room. 

“I will simply ask the human.” If you cooperate. You had been so eager before. What had changed? Granted, Gaster knew that his methods of keeping you here did not sit well with you. He could only be sorry. Science took more precedence over your comfort, loathe as he was to admit it. He was not, and would not, hurt you if he could help it. 

You stirred, after what felt like a ridiculously deep sleep. Your arm was stiff, you pulled it, realisation soon flooding into you as you grunted, groggily rolling your eyes and sighing. You felt as if you should be more frightened. He could tear you apart to find out what your insides looked like, if he wanted. The idea had you grow cold, as you gazed down at your bare legs.

“Ah, you are awake. Did you sleep well?”

The voice made you jump, Gaster’s shoes clicked along the floor until he was in your line of sight. You wanted to ignore him so badly, biting your lip and letting the silence drag on, until Gaster’s eyes were dim and downcast.

“I had been wondering if you would appreciate me bringing something from the surface world. To ease your nerves.” Gaster’s hands had unclasped, ghosting over his lab coat carefully, waiting for you to speak. Now the silence had started to bother you, too.

“...I want to go home.” You spoke so quietly, Gaster’s smile dropped entirely, fingers fell to his sides, and he sighed softly.

“I know you do. I am offering to help settle you in, but there is little more I can do.”

“You could let me go. I shouldn’t have found you in the first place. This was a mistake. I’m going to die here.” You could feel Gaster’s watchful stare on your face, and you willed yourself not to start crying for the umpteenth time.

Gaster had slowly started to take notes, and you grew furious. That _insensitive_ asshole really didn’t care. 

“Are you even listening…?”

“I am. I have never seen a human weeping. May I come closer?”

You felt embarrassed that he had caught you, he took your silence as confirmation, before he was kneeling beside you. 

You had never seen him this close. Instincts told you to struggle. The way his eyes flickered and shivered like fire, studying your face. You flinched when a bony finger pressed just underneath your eye, squeezing the tear from you. It was unsurprisingly cold, but much smoother than you had assumed.

“Fascinating.”

He uttered, his finger ran down the streak of wetness and inspected the tip, as strange floating hands jotted notes behind him. 

“Will I ever be able to go home again?”

Your voice had jarred him out of his thoughts. He was so close, watching the way your eyes burned into his sockets, he frowned slowly, sadly, finger retreating from your face.

“I must insist you stay, for my experiments.”

“What if...I go home, and you can just pull me back for a little while a day…?” You had given it thought. If he was able to rip you from your room before, he could do it again. 

“It exerts a lot of my energy. To continuously rip open doors through space to push and pull a living creature through is much more work than I make it seem.” He stifled a sigh, not wanting to breathe on you. You and him remained side by side. You could see the cracks clearly in his skull, dipping into a shadowy blackness. You hated to think you could finger it, press into his head, but it seemed so deep and open. 

“You asked me if I could have something from home. I want my phone, please.” You had to let people know you were alive. You wondered if your friends were freaking out. “Will it work? I...the last time I got near you, it broke.”

“I’m unsure. I will do as you ask and retrieve it.” Gaster stood, his coat lifting off of the ground as he blinked out of existence, returning seconds later, clutching your phone. A horrendous static noise thundered into your eardrums, and you winced.

“You do make it look easy.” 

“Ah, thank you. I am not without my talents, it would appear. Before I hand this to you, may I take a look at it?” He seemed hesitant to give it to you, and you relented, huffing a soft agreeing response, before you heard the soft tap of bone against glass. 

“Utterly fascinating. We had nothing quite like this. I assume it still has the same functions as a usual phone? Calling, the ability to pull items through it and so on?” Gaster’s eyes burned and shuddered excitedly, glancing up to look at you as he pressed a button, satisfied with the click. He had found how to turn the screen off and on again, before passing it to you carefully, crouching to inspect what you did with it.

“Oh, no. Your phones are different. We can call, but we can’t pull things around.” You were too used to using both hands. Gaster stiffened at the scene, his hand rested on the thick chain.

“Please, promise me you won’t start running from me if I untie this.”

“Where would I be able to go…?” You had lost hope in trying to escape. He was your only way out. He seemed to contemplate your resignation, before uncuffing your wrist. Your arm clicked as you pulled it down, relieved at the feeling, before you opened your phone screen. Dozens of missed calls and messages sent your heart racing. “Fuck.”

“Is something the matter?” Gaster sounded genuinely concerned, and you glanced towards him.

“My friends probably think I’m dead in a ditch somewhere.” You groaned, before sliding your finger over the screen and unlocking it, ignoring the soft gasp from behind you. “I have to call someone, okay?”

Gaster refused to leave the room outright, but stood beside the doorway from the bedroom to the main hallway, writing notes as you pressed the phone to your ear.

_“Where the hell have you been, punk?!”_ Undyne’s voice rang in your ear, you bit your lip and fought back your tears at hearing the voice.

“Undyne, I’m okay. I...I really can’t explain.” You could tell them everything. Get them to look for you, use it to escape. As Undyne yelled into the phone, you could see Gaster watching you silently. “I...decided to go on a vacation. In private. I just wanted some time to myself.”

_“You scared the fuck out of everyone, you stupid-?!”_

The phone was taken away, you heard the slam of a door, and the muffled voices distant in the background. 

_“where are you…?”_

You had missed Sans’s voice, fiddling with the covers under you. 

“...Gaster tore me through the wall in my room and he’s keeping me here and he won’t let me leave-” You heard your phone shut off, bringing it to face you as you tried to call again. Gaster looked at you, and you felt your body grow cold, his eyes were boring into you, and you dropped your phone meekly, letting it sit on your thighs.

“I don’t understand you, human. You had been so keen, once. So curious. And here I was hoping we shared a lust for knowledge.” You felt scolded, fingers pressing the buttons on the side of your phone in a vain attempt to distract yourself from his hard stare.

“I don’t want to be here-”

“Then why did you _bother_ in the first place?” He snapped, irritated. His arms folded neatly and you shrunk at the clipped voice, the reverse echo cut just as short. 

“I wasn’t afraid before! I thought I could expose some stupid rumour. But I started having nightmares, and got convinced it was all a shitty idea. Which was more than proven right.” You tried to snap back, fingers lightly pinched your jaw, holding your head in place. Smooth bones along flesh, your eyes widened as if you expected him to finally lash out on you.

“I would like to start my experiments now. I need your consent.”

You were silent. His fingers left you, and he waited. You sat up, legs swinging over the edge, thumbing your phone screen and watching the smear of your prints stretch along the glass.

“Okay…” You agreed. A hand pushed your back, and you stood. You had wished you could have asked him for clothes. Your legs felt too exposed, pulling on your shirt with one hand, as the other clutched your phone tightly, not willing to part with it.

The walk was silent. Gaster’s form was lithe and spindly, you could see the back of him, hands clasped firmly together, his spine straight as he ambled in front of you. The hand at your back never left, urging you to follow.

Without prior warning, a hand scooped you up. You let out a yelp of surprise, before you were sat on a medical bed, your arms and legs held firmly by smaller hands. 

“T-This is starting to scare me, Gaster.”

“...I will not harm you on purpose. I will tread lightly, and if something causes you discomfort, you must let me know. I will be conducting a physical examination. As you are most likely aware, your body is much different than a monster’s own. If you grow too uncomfortable, I will cease. However, know now that I will want to return to the places I have not explored. If you truly wish to be gone so quickly, I suggest you...ah, what is the phrase? Tough it out?”

The thought was unnerving. You really hoped he wouldn’t hurt you. Another small pair of hands scribbled notes behind Gaster, and he moved round to your side, stooping to examine your face.

“May I examine your head?”

You nodded silently, glancing to the hands that remained by the desk.

“How many of those can you make?”

“As many as I need. Though I’d stop at say...29. 30 seems rather much.” He smiled politely, trying to ease your nerves. You couldn’t help but to feel as if you had heard that before. You didn’t have enough time to ponder for long. Fingers stroked along your cheek, careful and soft, shifting up to stroke along your nose, slipping to your cupid’s bow, pausing at your upper lip. 

He soon continued, after your gaze started to shift to him, curiosity garnering the better of you, you watched his eyes waver.

“Please open your mouth.”

You weren’t sure you were as comfortable with that. _Tough it out_. His words nearly made you openly roll your eyes, you complied, hesitantly opening your mouth, feeling a finger press inside.

“Ah. I’m unsure why I was expecting it to be more firm.” Gaster muttered aloud, and you snorted an accidental laugh at the half bewildered expression he was making. His pupils flicked as he looked at you, before smiling nervously. “Was that amusing?”

“A bib.” You spoke around his finger. Your tongue tried to stay flat at the bottom of your mouth, but you couldn’t resist squirming it, the intruding poking was irritating. You could taste absolutely nothing, as you held your mouth open, drool pooled in your mouth, and he inspected it, dipping his finger into the liquid and pulling away, a small string connecting his fingertip to the inside of your mouth for a moment.

“Interesting. Subject has a trigger response to lick my finger. Reason is currently unknown. Prolonged opening of the mouth causes it to fill with a thin, watery liquid.” He watched his hands write, and you swallowed the rest of the spit, pulling a face. 

“It’s called spit. Or drool, I guess.”

“...Spit. I believe some monsters have a similar variant. Your teeth are rather small, aren’t they?”

“Well, compared to you, they might be. They’re pretty normal teeth.” You would stroke your mouth, had your arms not been held.

“I see. Interesting. I am going to continue touching you.” He stated and prodded at your hair, running his fingers through it. For a moment, he seemed lost in the feeling, smiling fondly as strands curled around his phalanges. “This is pleasant.”

You could feel your cheeks grow warm. You were slightly repulsed by the fact he had made you blush. Shouldn’t you be angry? He had kept you down here against your will, he wouldn’t let you leave. 

And yet, he made no intention of hurting you. And even collected your phone for you. It was a strange kind of feeling. You were much calmer, as he started to stroke your neck. 

You hadn’t felt such a strong surge of tingling in too long. You uttered a soft hum, eyes closing before you had noticed he had stopped.

“Are you in discomfort, human?”

“Oh...no, it actually feels quite…” You stopped yourself. Gaster half frowned in confusion, but you had not said it was uncomfortable. He continued, and your eyes slid closed.

Gaster felt your collarbones, pressing lightly against them. He inspected your shoulders, arms, curling and uncurling your fingers. He was pleased to hear no objections from you, but you had looked as if you had dozed off. Gently, he nudged you, and your eyes fluttered open.

“What’s wrong…?”

“Ah, well, you looked so comfortable I had thought you to be asleep.” Gaster chuckled, and you blushed. Did you truly look so relaxed? Admittedly, you were finding it difficult to be anything but. You twitched when his fingers dipped below the neck of your shirt, stroking your sternum. He stopped instantly, eyeing you.

 

“Did it hurt?”

“It’s not really somewhere I’m touched often.” You mumbled, and he gave you a look.

“Is there a reason? I will remind you that I plan to examine all of you, but if you are uncomfortable, I will stop.”

“No, it’s-” You were cut off, the phone in your hand buzzed unexpectedly, your grip loosening as it fell to the ground with an ugly clank. “ _Shit!_.” 

It continued to buzz, Gaster watched it vibrate along the tile before collecting it. 

“Sans…?”

His voice sounded quiet, the name fell out of his mouth, he looked at the screen before setting it on the desk, returning to you.

“D-Did you say Sans? He’s calling? Please, I have to-” Hands squeezed firmly around your ankles and wrists, not enough to hurt, but enough to convey Gaster’s refusal.

“Forgive me if I cannot find it within myself to trust you with a phone for now.”

“Then you can’t touch me any more. I withdraw my consent.” You frowned indignantly. Gaster’s eye flashed strangely for a split second, the hands around your limbs pooled together and scooped you up without hesitation, pulling you along and past your phone, towards the bedroom, sitting you on the bed. 

“You may do so. But you only delay your exit from here. I had been expecting a more mature mind, but you insist on behaving like a child.” He warned, a coldness in his voice that stilled you.

“...Don’t tie me onto the bed again.” It was a weak request, you felt the fear bubble up in you again. Though he had never hurt you, you could feel his ability to seeping into your skin. He huffed a sigh.

“I will not. You cannot leave, regardless. If you require me, simply call, I will hear you.” He seemed exasperated, striding off and back into the room you were examined in, fingers plucked the phone up and watched the screen glow with another call. 

He let the phone ring, the vibrations feeling unpleasant along his bones. He hadn’t heard the name in years. He laughed. A hollow, ugly echo stretched across the room as the phone was set down. 

“I do hope the human’s friends do not come looking. It is a great trouble to have to keep them out.”

**Notes for the Chapter:**

> Gaster gets a little touchy, in more ways than one, eh?
> 
> I think the depraved part will be soon. I can feel it in my bones. 
> 
> (Am I turning into Sans...? I might be.)


	8. For science, of course

**Notes for the Chapter:**

> Everyone is so nice, thank you all very much! I can't quite believe how much people are enjoying it, you're all wonderful!

You hadn’t slept. You had sat on the bed, angry, swinging your feet over the edge. The room felt strangely eerie without Gaster’s presence. Something you never thought you’d be telling yourself. You sighed, and after a while, the anger slowly started to melt, your stomach growling pitifully at you. 

“...Gaster…?” You meekly called out. You had loathed to utter the name, feeling your pride shatter in your lungs as the man leant into the doorway, unsmiling and still stern. You gulped quietly.

“Yes, human? Is there something you needed?”

“D-Do you have any food…?” 

Upon asking, Gaster’s expression softened, and he looked sympathetic. He held up a finger to signal you wait, which you did, patiently. After minutes, he was back, clutching a packet of instant noodles. He paused once he saw the half hearted look on your face.

“Is this not adequate? I’m afraid I am truly unsure on what humans eat. I had forgotten you needed to eat at all, actually.” He admitted with a laugh. You fought the smile on your lips. For a scientist, he seemed to lack common sense. 

“It’s fine, I just need to put it in some water and boil it. Do you...have anywhere I can do that?” You looked up at him, watching his pupils wobble as he pondered, before making an almost grimace at the realisation.

“There is a kitchen in the upstairs lab. If I...if I bring you there, do not try to run. The doors are sealed and you cannot get out, but I would like you to prove to me you can be trusted.” He watched you, picking your reaction apart as you fiddled with the shiny plastic of the instant noodle packaging, before offering a small nod in return.

“...Okay. Thank you.” You smiled sadly, and he offered his hand for you to take. He had never let you be the one to touch him. You felt hesitant, your fingers slipping over the smooth ridges of his phalanges, you squeezed them loosely, before you felt a painful rippling in your body, your legs giving out as you buckled, Gaster’s hands snatching your arms to prevent you from hitting the tile below.

“Ah, I should have warned you. I didn’t even consider.” Gaster frowned deeply at himself, as you clutched onto his coat, his arms half around your body as he pulled you back up with a soft sigh. “Please forgive me. I give you a lecture on trust and nearly have your head split open because of my neglect. You must think I’m quite awful.” He chuckled weakly, nervously eyeing you, as you steadied yourself and groaned softly at the whirling in your head.

“That’s not why I’d think you were awful.” You blurted, and he stilled. You had clearly upset him, and he fell silent, as you bit your lip tightly and looked at the ground. “...Sorry.”

“It’s...quite fine. May I lead you to the kitchen?” He spoke so quietly, you barely heard him. You couldn’t bring yourself to believe that it was okay, but you hummed a yes, and he began to walk, you following quickly behind, until you were both in the kitchen.

“Do you have a saucepan anywhere?” You broke the stale silence and he glanced at you, before opening a hand and fetching one out of the air. A strange green magic slicked his bony fingers and the pan’s handle was clutched tightly. You stumbled back at the display, mouth gaping as you stared between him and his hand.

“That’s...you just...made one?”

“No. This is yours, is it not? I can...grab the object from your home, pulling it through the same door you travelled through. Though it is less energy, it is still rather tricky, especially if the object is large in size. Or living.” He handed you the pan, and you gawked at it, turning it over and inspecting it. It had the same burns on the bottom, the scratches from constant use, you couldn’t believe it. You heard a soft laugh, turning to Gaster, as you fiddled with the taps, pouring water into the pan and setting it on the oven’s top, the heat flaring around it, the fire lapping at the curved base.

“...Why don’t you go to the surface world, Gaster?” You turned to him, waiting for the water to boil. He paused, and chuckled, fiddling with his collar idly.

“Time and space is an elaborate concept. Technically, I already exist in that world. Think of it as me existing in the cracks between your time and my own.”

“So you can exist there, too? So why choose to stay here?” You glanced at the water, watching the tiny bubbles start to form at the bottom. 

“I am familiar with it. This was my home, once. I’d like to think that it still is.” He sighed, eyes dimming in brightness. You opened the package, putting the block of noodles into the steaming water, before turning back to him sheepishly.

“I need a fork, please.”

He smiled, then. A warm, perhaps even genuine, smile. The fork was pinched between his fingers as he handed it to you, watching you break apart the noodles curiously, half looming over you to inspect the way you stirred the noodles. You pretended not to notice your personal space being invaded, hiding a smile as you added the flavouring and hummed to yourself, before your stomach growled loudly, and you blushed at the noise.

“...Does your body do that often?” Gaster questioned and you ducked your head, your cheeks growing embarrassingly warm.

“Only...when I’m hungry.”

“Ah, I see. I will make notes.” Gaster summoned a pair of hands, scribbling notes outside of the kitchen. “So, until you are fed, your body produces a noise to inform you that you are hungry?”

“S-Sort of, I guess. I don’t really know.” You had never been told. Maybe once in school, but you were quick to forget most of the information you were taught once the exams were finished. 

You finished, eating in a quiet hurry, trying not to create any sort of stupid noise, gulping down the noodles from the pan, you set the fork down once you were done, licking your lips. You had turned to find Gaster, only to see him inches from you. You jumped, and his eyes flickered in surprise.

“Oh, forgive me. I was watching you eat.”

“Ew.” You uttered, and he grew even more confused.

“You express disgust at this. Why, may I ask?”

“I just think it’s a little...gross? Eating is natural, but watching someone eat normally puts them off of eating. Maybe it’s a social thing.” You shrugged, and he hummed thoughtfully. You could hear scribbles in the background. “You’re really documenting everything.”

“You should not be surprised. Does it bother you? I can take notes in a quieter manner.” His consideration for you was starting to grow on you. It was almost endearing.

“It’s fine. I’m just not used to it. I have...a favour to ask, actually. Um, well, a few.” You tugged on your shirt. He looked nervous, eyes burning as he watched you fight to look up at him.

“Please voice your thoughts, human.” He offered you, and you hummed softly, more of a whimper, suddenly feeling selfish. You steeled yourself and took a deep breath, ignoring the scribbling behind you.

“If I’m staying here...I want some things from my home. I need clothes, and things to wash with. And...maybe something to keep me entertained.” You looked up shyly, and he smiled sweetly.

“Yes, of course. I would like for you to be as comfortable as possible, after all. Would you like your things situated upstairs or down?”

“Y-You’re letting me stay upstairs?” You blinked, surprised. He smiled nervously at you.

“Well, I trust you to be good enough. Also, the things you would require for daily living are here. I assumed you would find it more comfortable. If you’d like, I could even move a bed up here.”

He was being so kind. You couldn’t help but to be suspicious. He still wouldn’t let you leave. But he seemed so truthfully to want to assist you in being relaxed. He slowly ushered you away from his presence. He didn’t want you to be exposed to too much magic in case it affected his results. You heard a soft ripping, a pop in your ears and the white noise shuddering through your body.

You had a bed, your basket of soaps and shampoos on the left behind table from Alphys’s room. Your entire closet had been brought along, your clothes inside, you had to laugh at how much Gaster had put in the room. He huffed a breath, smiling at his work.

“Goodness, you have more items than I would assume. I took the liberty of bringing things from the entirety of your bathroom. I was unsure what you used, so to be safe, I took everything.” He was fiddling with your hairbrush, flicking the bristles in interest. “What is this?”

“My hairbrush. I...brush my hair with it.”

“...Aptly named. May I try?” Gaster held the brush up. You stilled for a moment, before offering a soft laugh and nodding. You had sat down on the newly moved bed, Gaster sitting beside you, clutching the brush carefully. “I hope it does not cause you any pain.”

“I like having my hair fiddled with. It can get knots sometimes, though. They’ll pull, so just be careful.” You warned softly, and he nodded, drinking in the information. Skeletal fingers took small sections of your hair and curiously brushed through. He was so gentle you almost didn’t even feel it. You started to lean into the touch, of soft strokes against your scalp, he brushed through slowly. 

“...Does this make you happy, human?”

“Mm…? Oh, yeah. It’s relaxing.” You half mumbled, and he smiled. 

You missed your things, admittedly. You dug around your closet and smiled at the new selection of clothes to choose from. They reminded you to take a shower, and you nodded to yourself in agreement. Gaster had slowly brought more and more over, until Alphys’s lab started to look like a condensed version of your apartment, with your things scattered about. He had even taken your paperwork, though you didn’t know if you should be thanking him for that.

“I wonder why everything still works.” You pondered as you found the shower, your towel and a fresh shirt and panties slung over your arm as you fiddled with the knobs, jolting back as the water turned on, pleased with your success. 

Everything worked as if no one had ever left. Electricity ran, the lights remained on, even the water grew warm in the pipes. You couldn’t help but to think that Gaster was running it all. But surely he didn’t have enough magic to do such a thing.

The shower was more than welcome on your bare skin. You washed and basked in the familiar smells of your soaps and shampoo, soon stepping out and towelling yourself as dry as possible, slipping on your clothes and smiling. You couldn’t quite believe you felt so...normal.

“Gaster? Are you down in the lab?” You peeked your head down into the pitch black depths of the elevator shaft, hearing nothing. You turned around and wandered slowly back, only to jump in surprise at Gaster’s figure in the main room. “O-Oh! You could have said something.” You huffed, crossing your arms.

“I did not want to surprise you into falling down the shaft. I was hoping to conduct more examinations today, if possible. I need your consent.” He had his hands behind his back again, his gaze faltered to take in the slightly darker colour of your hair, the new shirt on your body stuck to damp flesh as you gave him a small nod.

“Okay. Are we going down for that?”

“If that is alright. My lab contains everything I need to conduct experiments that will not alter my results. I hope you understand,” He fidgeted for a moment, before taking your hand, soon pausing. “Ah, would you prefer to be carried or ported?”

“Ported…? You mean like you did earlier?” You squeezed his fingers, the cool contact on your warm skin felt strangely nice.

“Yes. It can make those who are not used to it feel rather ill. I would perhaps insist I carry you.” He prompted, and you smiled, as a large hand formed behind you. 

You were scooped up between fingers, yelping in surprise as one slid between your legs. Gaster almost jolted, looking at you with bright pupils.

“Did I hurt you at all?”

“N-No! No, I’m fine! Just was caught by surprise!” You flushed, as Gaster hummed in worry, but did not question further. 

You both entered the dimmer surroundings of the true lab, you returned to the same medical table and was held down carefully, grateful for the pressure to be away from more delicate areas. Gaster had gone over his notes, before stopping by your side, smiling down at you pleasantly.

“I had gotten to the centre of your chest, before you had withdrawn consent. May I continue?”

“Yes.” You breathed, trying to relax. In honesty, this felt uncomfortable. Being held down whilst fingers stroked your skin and prodded at you was uncomfortable no matter what. You watched hands scribble notes by the desk, as fingers tugged at your shirt collar.

“I may need to remove this.”

“W-What?” You stuttered, your cheeks hot. You had been bare in front of doctors before, maybe once, but this felt entirely different. You stared furiously at your shirt in silent contemplation. 

“Is something the matter? I will not ruin it, I promise.” Gaster’s pupils flickered, and you swallowed hard, before breathing a small huff.

“O-Okay. Go ahead.”

He sat you up, hands slowly pulled the shirt over your head, and you pressed back down onto the medical bed, breasts exposed, you could feel your heart thump in your throat as his eyes gazed over your bare flesh. You didn’t know why you felt so nervous, he had given you no indication he was even remotely interested sexually. If he could even _have_ sex. Could he? You could scream at yourself for thinking of it at such a moment. Gaster’s hand returned to your sternum and you jolted suddenly, his hand pulling back as if he had stabbed you.

“Goodness, my apologies. Are you alright? You seem rather distressed.” He looked at your face, and you nodded quickly, trying to assure him you were fine.

“Yeah, don’t worry. Being naked just feels a little...intimate.” You admitted, blushing. Gaster nodded, scribbling notes.

“Subject reacts in a state of shyness at being physically exposed.” He mumbled to himself, audible enough for you to catch it, inwardly groaning at how utterly stupid that sounded. “May I touch you, still?”

You nodded, tense.

**Notes for the Chapter:**

> You can ONLY imagine what's coming next, right...? 
> 
> <3


	9. Getting closer

He prodded your sternum, and you winced in pain. He apologised, and you smiled. Everything was going surprisingly calmly, considering you were in just your panties with a strange existential outlier’s hand ghosting over your skin.

“Hey, Gaster? Can I ask you something?” As he paused to take notes, he smiled at you.

“Of course.”

“Did you really fall into...i-is that insensitive?” You shut yourself up. Despite your assumption, he did not frown at you. He continued to smile, even uttering a soft laugh.

“Sort of. In another timeline, I did not. The stories about me are both true and false. I am sorry to be such a headache. I know I can be quite the confusion to talk about. If it makes you feel any better, I am often just as lost.” He laughed sweetly, and you giggled. You couldn’t bring yourself to be frightened of him. 

You were about to speak, until fingers stretched along your breast, squeezing gently. You gasped at the feeling, your embarrassment crashing into you in waves. Gaster retreated so quickly you could hear a bone click in his wrist.

“Forgive me, I had not meant to cause you harm, human-”

“It didn’t hurt. J-Just surprised me. Cold fingers.” You smiled nervously. You couldn’t admit how oddly _nice_ that felt. How long had it even been since you last were touched like that? You’d laugh at how lonely you had been, if you weren’t so flushed. 

“Ah, forgive me. I shall use magic to warm my fingers, do not be alarmed. It will not hurt you, but may perhaps feel slightly strange to the touch. Are you ready? May I continue?”

“Y-Yeah, go ahead.”

It did feel strange. His fingers felt warm and like static, a numbing, pleasurable tingle running up your spine. Specks of green sparked as his bones shifted back down, cupping your breast and humming in thought.

“Do you know why you have these?”

“F-For milk. Babies, and stuff.” You murmured. Gaster seemed interested, and without thought, lightly pinched your nipple, before you gasped softly, twitching against the hands that held you down. He stopped.

“Did I hurt y-”

“No. I’ll tell you if you hurt me. Just...don’t worry, okay?” You assured, as he nodded slowly, trying to ease himself. He truly didn’t want to harm you. 

He repeated the same treatment to your other breast. You stiffened, tensed and let out a short breath as your nipple was pinched. Gaster hummed in thought.

“Subject’s skin hardens when stimulated.” He spoke. You looked up at him bashfully and bit your lip. 

Fingers dipped down to your stomach. You fought back a snort of laughter as he stroked your ribs, tickling you. He found himself laughing at your expression, and you blushed, giggling loudly as he purposely teased you, a heat in your cheeks as he smiled down at you.

You felt a strange sparking along your skin as he pressed slightly more firm into each space between your ribs, hands jotting notes at the desk, he reached your hips, smoothly stroking over the soft fabric of your underwear. 

“These are nice.” Gaster smiled, and you felt your eyes widen. Did he even know? He must not, surely. “I may need to remove them, however. I must examine you fully.” 

You were torn between dread and embarrassment. You knew it was different. You silently raised your hips and let your thoughts keep you silent. What if he thought you were gross? Did he even have a comparison? Fingers hooked around the edges and pulled down, you felt your entire body flush and scream in a furious mortification as he looked at the soft curls of hair. 

“Do you use a hairbrush for these, too?”

A moment of silence followed, and you felt lightheaded, before you laughed too loudly, nervous.

“N-No. I have to tell you now that it’s a private area and babies come from there and I don’t just let people randomly touch it so don’t be surprised if I jump or react a little strangely in fact just take it as a sign that I’m perfectly fine, okay?” You babbled helplessly, and if he could blink at you, he would have. 

“...Are you okay? Should I be touching you here? I know eventually I must to continue my research, but if you are truly uncomfortable, I can stop.” Gaster was genuinely worried, your eyes seemed to be gazing anywhere but at him, your body stiff and rigid. Perhaps he was hurting you after all and you were just trying to be brave.

“Please just don’t think about it. I really am okay. It’s just...sensitive,” You had to tell him. You had to say something about how ludicrous the situation was. “And sexual.”

“Ah, I see.” Gaster nodded. You didn’t know why you were so surprised to see him understand sex. He was an adult, and a scientist, it should be obvious that he’d know. And yet, you blinked, shy.

“I’m just embarrassed.”

“So, rather than hurting, you feel pleasured?” 

You wanted to curl up. It was horrible to have it spoken so plainly in front of you. Gaster looked so unfazed by it. You nodded quickly, worrying at your lip in your nervousness. Gaster had to chuckle, seeing you look so daunted.

“It’s a natural response, yes? Have no concerns, I am not about to judge you. I have seen many different bodies in my time, mind you, they were not human. But some monsters have similar...erogenous zones. Tell me if you become too uncomfortable. I will resume touching you.” 

Though he tried to soothe you, you felt no better, feeling a strange tingling over your mons, fingers pressing against the soft flesh. Your hips twitched, he smiled at you in an effort to keep you calm. 

A finger slipped between your outer lips, and you squeaked, jolting against the hands that held you. Gaster paused. 

“I am aware it does not hurt, but is it uncomfortable? I would not like to push you too far.” The finger was still against your inner folds, and you tried not to squirm as the magic pricked against your skin.

“N-No, go on. I’m fine.” You smiled weakly, your nerves getting the better of you as the finger proceeded. 

He rubbed your inner labia, feeling the wet flesh carefully as you tried to keep still, biting your lip and closing your eyes. 

“Oh?”

He sounded, confused. You opened your eyes and tensed, seeing Gaster’s head looming between your legs. Fingers slowly stretched you apart for him to examine you better, as he pulled back your clitoral hood and lightly prodded your clit, earning him a surprised twitch and a gasp from you.

“It’s all rather intricate. Subject responds to touches by creating more of a slick liquid, reacts by tensing when I stroke here,” He paused in his muttering to give your clit another rub, confirming his suspicions. “It also starts to grow firmer. Very interesting.” He nodded, eyes focused on you. 

He massaged along your inner labia for a while, applying pressure and watching you react, nearly yelping loudly when he put a slight pressure on your clit.

“So, this small hole is for reproduction? I can’t imagine anything coming out of such a little orifice.” He poked at it, before feeling the tip of his finger press inside, nearly gawking stupidly at the feeling, before pulling back. “That was...interesting.”

You felt ashamed that you were so turned on. It had been a while, sure, but a skeletal monster poking at your parts shouldn’t be so arousing. 

“It’s not...just for reproduction. You can masturbate or have sex recreationally…? I sound so stupid, this is all really weird.” You groaned. 

“You may stimulate yourself simply for pleasure, and not just for creation? Is this common?”

“Pretty common, yeah.” You smiled. You felt so worked up, you cursed yourself for feeling so tightly wound. He left you alone enough to work on your thighs, magic dancing along your skin. You hated yourself for being disappointed. You hated yourself for wanting his fingers back against you, he must have caught you staring, he looked up at you in confusion, hands releasing your knee.

“Are you feeling well, human? Would you like me to stop? Ah, are you tired?”

“...Yeah, I’m a little tired.” You smiled, and he returned the expression, fetching your shirt and handing it to you as the hands vanished from your limbs, watching you redress and pull your panties up, thoroughly dissatisfied. Why, though? Shouldn’t you be happy that he had no ulterior motives? 

He scooped you up in a hand, smiling as you and him both returned to the upper level, setting you down. 

“Gaster? Do you ever get...I mean, can you get pleasured? Is that too personal?” You were prepared to defend yourself with the excuse that you were simply curious, your face warm as you pulled on your shirt, nearly stretching it beyond repair.

“Well, yes. Not how you do, though. I rely on magic. Actually, truth be told I am unsure now. It has been a long time since I...well, you understand. I have not had the chance to see if I am able. Forgive me for not being able to provide you with a perfect answer.” He chuckled as you giggled awkwardly. You weren’t sure what you were expecting. The idea of Gaster being aroused was a strange image in your mind.

“I bet you were a real hit with the ladies.” It was the first time you had tried to laugh with him. You had worried he would be offended, a strange green glow rang around his eyes as his cheekbones started to glow in the same colour. 

“O-Oh, um, not quite. I was a very busy- I was very busy and I had little time to socialise- that is to say...well, you probably catch my meaning.” He laughed nervously, tugging at his collar. 

He was cute. You frowned at yourself for even thinking it, but you couldn’t deny the softness in your heart for the way the strange, tall monster grew so flustered.

“Nah, I bet you were really popular. All the lady scientists swooning when you walked by.” You winked, teasing him. He blushed brighter, pupils flaring with an odd green fire as he tried to laugh it off.

“You’d be utterly disappointed to know the truth, human. You should be resting.” He changed the topic, a hand to his mouth as he cleared his throat. You stood still, smiling. 

“Make me.”

“Excuse me…?” His pupils receded in colour, he looked confused.

“Not up to the challenge, ladies man? Not everything has to be work.” You had no idea what you were doing. A swelling mixture of sexual frustration and boredom had festered inside of you, and you were determined to take it out on Gaster. Teasing him seemed to wield the best results, as his gaze became restless.

“Um, well, I don’t want to force you to rest. I don’t want to force you to do _anything_. You’re very lively for someone who said they were tired minutes earlier.” He smiled, and you half grinned at him. 

“What do you do for fun, Gaster?”

“I research. It is very interesting.” You deadpanned at the response. He lowered his smile. “You do not feel the same, then?”

“Finding out certain things can be pretty interesting. But I mean...do you watch movies?”

“I do not.” He replied bluntly.

After gentle persisting, you had managed to get him to give you your DVD player, bringing your entire collection with him, as he was unsure which ones you’d like to have. You smiled, looking over the covers.

“Watch something with me?”

He fiddled with his coat, and sighed, nodding. It had taken you a few attempts to hook the player up to the huge monitor, until Gaster had simply rearranged the wire composition entirely, as you side-eyed him for his creativity, he simply laughed at your faded scowl.

He had asked so many questions during the movie, halfway through, you found yourself watching his hand. Skeletal fingers idly stroked his coat, the holes in his hands were abnormal, but no longer unsettled you quite so much. Without much thought, you took his hand, startled at your own actions as Gaster jumped, looking at you.

“Did you need something, human?” His pupils watched you grow nervous.

“I...can I touch your hands? I know I should have asked before but I don’t...know what came over me. Sorry.” He smiled, offering his hand silently. You were surprised it was so easy to get him to comply, but thinking on it, he was often trying to make you happy. The thought made you smile, warm fingers against cold bone, you ran your finger over the ridges of his knuckles.

“It feels nice…” You mumbled to yourself, as Gaster laughed weakly. “I’m sorry, this is really personal.”

“If I were to examine you without letting you do the same, I’d be a hypocrite. You are quite free to touch me, and if I am uncomfortable, I will tell you to stop. I trust you will treat me the same as I, you.” 

Your fingers moved from his hand, stroking his cheek lightly, nodding. He felt so much warmer here, magic seeped through his bones as he blushed, pupils watched your hand carefully. You ghosted over the dips in the cracks, wincing at them. 

“Do they hurt?”

“No. Perhaps they did, once. But not now. I do not recommend putting your fingers in, though.” He laughed, and you smiled with him, shuffling closer. You cupped his cheekbones and smiled, slowly straddling his lap, finally getting a close look at his eyes.

One pupil was larger than the other, green fire rippled and flickered in a ring around the white, and you found yourself caught in the way they shuddered.

“N-Need I remind you, that is in fact my eye, still. You’re...staring right into my eye.” Gaster shifted nervously, his bones warm against your palms. You tore yourself away, cheeks burning.

“G-God, sorry. I totally forgot. They’re so pretty.” You blurted out, and Gaster laughed unexpectedly loudly, making you jump.

“Forgive me, that was quite the genuine compliment. It caught me off guard. I had not meant to startle you, human.” His hand was on your lower back, thumb pressing into your spine gently. 

Maybe it was a mistake to press your lips to his mouth. You felt utter stillness in him, pulling back as you sat on his lap, your eyes focusing on the front of his coat. What were you _doing_? He had stolen you, kept you prisoner, denied you access to your phone to call for help. You couldn’t go home because of him. 

“...Human?” He watched you, lost in thought, and you smiled sadly, embarrassed and shamed.

“That was really gross. Of me. Not you, you’re not gross. I’m sorry, maybe I am tired after all.” You muttered, and Gaster glanced up at you, rubbing your side in an attempt to soothe you.

“I don’t know if I can comfort you. I am still unsure as to why you kissed me. But I didn’t...dislike it.” He chuckled. You looked shyly at him. 

“Can I do it again?”

**Notes for the Chapter:**

> Don't be too mad at me being a little bit of a cockblock. //shields self
> 
> But the depravity is coming soon! (Ha, coming. Get it? Ugh, I really think I might have Sans syndrome.)


	10. How nice of you

**Notes for the Chapter:**

> Here it is, the reason why this fic is rated E! I hope you enjoy it!
> 
> And if smut's not your flavour, this chapter is also skippable! 
> 
> Have a good time. <3

You kissed him again. This time, without surprise. You pressed your lips to warm bone and felt his hands hold your sides as you lifted yourself off of his lap enough to be equal to his face. 

Something wet touched your lips, and you pulled back, startled. 

Gaster seemed just as surprised at you for having such a reaction. You saw the faint glow from behind his mouth, and arched a brow. 

“I’ve- you have a tongue?” You blurted the question out, and he offered you a small laugh.

“Well, not the way you do. It’s made of magic. I still feel with it, but I can’t taste anything. It’s for...these types of things.” He gestured vaguely behind you, and you nodded, trying to grasp an understanding of how monster magic actually worked. Especially monsters that technically only sort of exist. You decided it was best to leave that out. “Do you not like it?”

“No, keep it. I like it.” You breathed, and he smiled, before you were kissing him again, your mouth parting to accept his tongue. The inside of your mouth immediately felt an almost numbing sensation, his tongue writhed along your own as you vocalised a whine, he paused, about to pull away to ask if you were okay, but was held still by your hands at his collar, gripping tightly and trying to deepen the kiss further.

You pulled away, panting. Your cheeks were hot, red hot heat rippled through your body as he smiled nervously, silently asking if the feeling was alright. 

You stood suddenly, pulling him to do the same, as he followed your lead, he tensed upon realising you were sitting on your bed, patting the space beside you.

“Are you sure you’re comfortable with this?” Gaster still sat, as if he was hoping you wouldn’t change your mind, watching you take his hand and straddle his lap once again, feeling bones shift under you as you pressed a kiss to the cheek that wasn’t cracked.

“I’m sure. Are you comfortable?”

“I am. I don’t want to hurt you.” He confessed, and you bit your lip to keep yourself from laughing in his face.

“Have you hurt me before, Gaster? I’ll say if I’m hurt.”

He couldn’t quite understand what had come over you. He was sure you hated him, and maybe you still did. Maybe you were doing this as some kind of human punishment. Gaster had many theories, too many, as his tongue pushed back into your mouth, having your body flush against his own, huffing a laugh as you raised yourself to level with him.

“You’re tall, shut up.” You pulled away, feeling his laugh, though your words were soft and you smiled. He patted your lower back.

“Forgive me for towering over you.” He smirked. For a moment, you were stuck on how to continue. He was completely unlike a human man, even more so. You paused for a moment, before taking the hands at your back and sliding them up and under your shirt, feeling cold bone cup your warm breasts, shivering at the feeling. 

“Just...do what you did on the table.” You laughed. It sounded much dirtier all of a sudden. Fingers sparked to life, magic thrummed against your skin as he squeezed and massaged you gently, that familiar static felt amazing against your bare flesh, before you felt another pair of hands start to pull the hem of your shirt up.

“May I?”

“...Yeah.” You had to laugh. He was so oddly gentle. He even stopped to ask to undress you. You knelt up as the shirt was taken off, leaving you in your panties once more in front of him. His fingers stroked along your ribs, gently resting on the hem of your panties. 

“Your body is so fascinating, human.” He marvelled at every twitch, stroking over every curve and dip, urging you closer to flick the tip of his tongue against your nipple, earning him a subtle noise.

“Your tongue is green.” You groaned inwardly. He looked up at you and laughed, before snaking his tongue out entirely, much longer than yours, you shuddered as it slipped back inside of his mouth. You could imagine where you’d like that to go.

“My magic is green. Can I remove these?” He tapped on your cloth covered mons, and you nodded, before pushing off of him suddenly.

“Wait, let me lay down. You can get on top.” You shuffled onto the centre of the bed, resting comfortably against the pillow, waiting for the right moment as Gaster turned to spread your legs, gazing away coyly as he burned bright, watching you. 

He was between your legs, your panties slowly peeled off and dropped to the floor, as he doubled over you, lapping at your neck. You could feel the magic against your skin, trying to find some friction as you rose your hips to press into his lap.

His fingers pressed along your inner lips, rubbing and lightly pinching the sensitive flesh, gently pulling back your hood and rubbing your clit carefully. You squeezed your thighs against his hips, groaning low in your throat as you felt a stronger pressure against your outer lips. The pressure was _incredible_ to grind against, rolling your hips slowly as you built up a pooling warmth in your stomach.

“You’re really quite wet.” Gaster smiled, fascinated. You nudged his shoulder slightly, frowning at him. He laughed, apologising as he urged a finger inside. He felt your muscles tighten and spasm around him, curling it slightly. You huffed and squirmed, trying to earn more of the same feeling as before. 

“It feels really good, Gaster...just, put another finger in.” You urged him, and he responded, another bony finger joining the first, a strange tingling had you biting your lip and closing your eyes, feeling him drag against your insides as he fingered you. It took him a moment to hope you weren’t in pain, upon seeing your lips slightly parted and your eyes half lidded, he smiled to himself. 

You weren’t expecting him to finger you so well. He studied your expressions and read the way you twitched slightly more when he angled his fingers a certain way, until you were clinging to the bed sheets below you and fighting back loud moans, gasping and grinding into his hand.

“O-Oh, fuck, Gaster, _Gaster_ -!” He squeezed his tongue into your mouth, the warm static numbness flooding your own tongue, swallowing a thicker kind of drool from his mouth down your throat, sucking on the tip as he huffed a soft breath, blushing. “A-Aah, fuck me, please.” You could feel yourself cringe at your desperation. Before you realised that he might not even be able to.

“...May I?” 

He seemed nervous, fingers unbuttoned his coat, as a phantom pair of hands slid it from his shoulders, leaving him in some kind of turtleneck and dress pants. 

“It’s not the same as a human body. It’s magic, but I’m assuming it won’t look too different.” Gaster truthfully had no idea. You sat up, curious to see. He almost wanted to stop you from watching, but he knew better than to deny you the knowledge.

It was the first time he had summoned genitals onto himself since becoming what he now was. You grinned at the soft green glow, giggling as it twitched. It was thicker than a human’s might be, throbbing with a magic that had you curious to have it inside of you. You laid back, legs spread, letting him hover over you and smile anxiously.

“I do hope it’s not too much, human.”

You felt so wet. So wet, and hot, and he was pushing the thick head inside and you couldn’t stop the whine from leaving your lips as he continued to push. You felt the hot burn of being stretched open, the strange tickling of magic dragging into your body, huffing as he buried himself inside of you, one pair of hands on your hips as his real hands supported his weight either side of your head, until you were pulling him down to kiss along his cheeks, not bothering to miss the crack in his face.

He wanted to move so badly. The magic in his body burst in ripples as he fought to keep still, wanting you to adjust. He panted softly against your neck, humming when you finally started to roll your hips. 

He slid out, to the tip, before shoving himself back in, as you had no time to hold back a moan, feeling the thickness throb against your wet insides, muscles tight around him as you arched your back, hissing through your teeth as he thrust again. 

The rhythm of his thrusts had increased quickly, a slick noise coming from between your legs as your limbs wrapped around Gaster tightly, half shouting the lab down as he massaged your clit and nipped at your neck, tongue lapping over the marks on your skin. Every noise he made, you basked in. Normally so quiet, hearing him grunt and groan against your ear had you more than a little turned on. He sat up, dragging your hips to him, once again looming over you as he shifted your hips up, your lower back lifting as he fucked you into the mattress. Your shoulders ached immediately, but you couldn’t complain, seeing the way Gaster’s pupils dilated and burst with magic, green pooling around his sockets as he rose in volume, gripping onto your thighs hard enough to leave marks. 

“I-I’m coming, Gaster, I’m co-coming-” You brokenly tried to speak, feeling his thickness bury itself inside of you, coming out halfway and slamming back inside, jarring another squeal out of you.

“G- _Good_.” He laughed, the echo grew to bounce around the room, his tongue poked out from his open mouth, the scientist panting hard as he felt you start to tremble and grind, his fingers worked over your clit to have you gasping, until you were coming, your orgasm spasming your muscles as you gritted your teeth, trying not to outright shriek at the feeling, for fear of startling Gaster.

You were shoved into, for a moment, you could hear something like singing, Gaster’s eyes swirled so brightly you had to narrow your eyes, his cock pressed tightly into you, you felt a hotness seeping into you, before he slowly pulled out. 

You were exhausted, your fingers slowly came down to touch yourself, feeling the hot liquid ooze out of you and onto a finger, bringing it up to inspect it, only half surprised when it came out green. 

Gaster was rattled, his magic dissolved as his eyes still flared strangely, trying to focus on you as he absentmindedly smiled.

“Well, at least I know I’m capable.” He laughed sweetly, as you hummed in response, feeling genuinely tired for a change. 

“Do you sleep, Gaster…?” You mumbled out, feeling yourself be scooped up, set back down with a blanket on top of you.

“I do not, no. But I will be resting. Magic exertion is quite tiresome.” He laughed again, in high spirits, before noticing you had dozed off completely. He stood from your bed, watching the subtle rise and fall of the lump under the cover, before smiling.

“Rest well, human.”

**Notes for the Chapter:**

> Eh? Eh? Was it everything you had dreamed about?
> 
> Well, be ready, because after this? Things are gonna go d o w n. <3


	11. Or perhaps not so kind

**Notes for the Chapter:**

> A big thanks for all the attention this has! You guys are quite simply wonderful <3 (Also you're free to bug me on Tumblr because I want to love all of you a lot)

In some timelines, you genuinely liked Gaster. In others, you had never heard of him. The idea that millions of you existed all at once and at the same time was fascinating to Gaster. He could pull one timeline’s memories and thoughts and interests, and just...put it into you.

He wasn’t going to tell you he had done so. Sex was unexpected, but he would play along. Pretend. It made you happy, and your willingness was needed for his continuation of his experiments. He had not hurt you, and perhaps it would not hurt you to continue. He wondered if he should return your original feelings. Back into the main timeline from which you first met and had been frightened. He frowned.

He couldn’t risk having you run away again. You would simply have to be content in ignorance. He scribbled notes down, stacking them neatly, before hearing soft noises upstairs, pausing to look at your phone with an apathetic laziness.

Perhaps he should erase Sans from your knowledge. A timeline in which you never met him, and yet still destroyed the barrier. A universe in which Sans did not exist, but life functioned perfectly without him. What an interesting theory.

“Gaster…?”

He ported quickly, watching you wince at the noise, before offering you a kind smile.

You smiled back, having been in the shower, you fiddled with your shirt. You had dressed up in more than just a shirt and panties, today. Gaster noted silently.

“Did you rest well?” Gaster’s voice was warm, and you smiled, nodding.

“I did, thanks. I’m pretty hungry, though.” You admitted with a soft laugh. Within minutes, you were cooking, Gaster watching you with interest. He jotted notes and watched you eat, and for some reason, you didn’t mind. Something was bothering you greatly, yelling vague nonsense in the deep pits of your mind as you chewed in thought.

“Is something the matter, human?” Gaster could see your pondering, and you glanced at him, swallowing and biting your lip.

“I don’t know. Something feels a little strange.” You confessed, and he paused. There was no way you could feel such a thing. You shouldn’t be feeling that. He still smiled, though slightly more strained. 

“Ah, truly? Would it help you to talk about it?” Would the timeline he had altered into your soul be rejected? He burned with questions, none of the answers came simply, and you fidgeted as you tried to word your feelings.

“When I first met you...I can’t remember it. I used to. I’m sure of it. I’m sure I remember the room, and you being in there. But everything else seems so blurry. Some of my memories seem so weirdly hazy. Maybe I’m just still tired, but it feels a little weird. I noticed it when I woke up.” You finished your food, and Gaster eyed you carefully. 

How did you _remember_ anything at all? How did you manage to retain any knowledge of a timeline that had been altered? A clever anomaly indeed.

“That is rather perplexing. I hope you are not too bothered by this.” Gaster frowned, a hand came to play with your hair, and you laughed weakly. 

“It’ll pass.” You returned, and let the conversation dip into silence. You missed your home. You had all of your comforts, but you missed your friends. It had been a long time. But your head started to hurt when you thought about them for too long. It felt as if your mind was working against you, stopping you from thinking about anything outside of the life you had now. Not to say you weren’t happy.

Were you?

From your apartment, Sans had noticed most of the things gone from your rooms. He had been panicked enough when you vanished. You had urged down the phone that Gaster had stolen you, and it had been too long spent trying to convince everyone else that you were fine, and that Sans was going to get you. Alphys had stopped believing him. Sans could feel magic bubbling in his soul, growing with each passing day you did not reach out to them. 

“A-Are you really going to find him?” Alphys walked through the city with Sans, who had stuffed his hands in his pockets. Sans had lived in too many timelines to watch you disappear forever. He had fallen in love with that soul of yours, the fighting determination that whirled inside of your body. You were unlike anything he had known. And you could remember the timelines better than he could.

“i’m doing something, alphys.”

“Y-You might get hurt. What about P-Papyrus?”

“i won’t be long.” Sans tried to reason. He was grossly worried for his brother, feeling the prickling phantom sweat bead on his skull, pinpricks watched Alphys pause at the outskirts of the city, watching Sans’s back.

“B-Be...careful.” She half breathed out. Sans didn’t bother to turn around, focused, he made his way to Mount Ebott.

He was good at his little ‘shortcuts’. Ripping cuts in space, slipping through and manipulating the fabrics to make it easier for him to get across. It was lazy, admittedly. Once far enough from the city itself, he ripped open a door, peering through. He hated the sight of the Underground. He was convinced he would have spent an eternity being reset down there. Stepping through to Waterfall, he was back at his stand. Memories flooded him and he silently ran a finger along the old, abandoned wood. 

He didn’t want to risk manipulating space too close to Gaster. Though, maybe now it was impossible. Sans assumed he was either in the Core, or the old lab. The Waterfall was a good enough start. He was going to get you back. And he was going to kill you himself. He warned you about the consequence, he could hardly believe you had wanted to do it anyway. 

Gaster could feel his magic twisting, shifting as he watched you doze off. Something wasn’t right. Once you had settled in for a sleep, he retreated into the lab, rolling his eyes. Maybe some kind of flare. That flower was still here, after all. Gaster felt rather sympathetic for the thing, knowing the feeling of being trapped in existence. Alphys had truly caused some grief. He half laughed. He knew about the Amalgamates, the monstrosities born to a life of suffering.

“I didn’t expect the King to lower his taste quite so drastically.” Gaster muttered to himself. He liked to think he wasn’t arrogant in his confidence for his ability. Alphys was good with metal, her robotics proved that. But what good were robots with souls? They were no substitute.

He sighed, basking in the dim light of the true lab and idly writing his notes, buried in thought. There had to be some way in which he could safely make you forget about the other timeline entirely.

At first, Gaster assumed it to be enough to grab the timeline in which you truly liked him and merge your memories together, enough to not have to affect any other aspect of your life. You would retain your personality, your other memories, the only thing changed would be your feelings towards him. But you were _fighting_ it, unknowingly, you tried to challenge yourself to remember parts of both timelines. Gaster worried it would drive you insane trying to pick apart your own head. Logic dictated that one timeline would have to go in order for you to settle.

He made his choice. He would remove your previous timeline, the one where you are afraid of him, and replace it with the better one. You would not be hurt, but he wondered if there were certain things you would see that would end up being a trigger back into the old timeline. Gaster knew you well enough to understand your retention of knowledge even after a timeline has been erased. You were a complicated little thing indeed.

A jump of magic. 

Gaster twitched, feeling its pull against his being, frowning deeply. Something was definitely amiss in the Underground. He wanted to investigate, but you would eventually wake up. He wrote a note, realising how hard human language was to write. Something simple, explaining he was gathering samples, and would return. Nothing to worry you over. The note was placed beside your bed, on the table and in plain sight. 

He made sure he was far enough away to port, the noise would have woken you otherwise. 

Somehow, Gaster was not surprised to see Sans. Given the amount of calls, it was a matter of time before he would show up, trying to invade in matters that were not _his_ place.

“So good to see you, Sans.”

Gaster became a reality, looming over the shorter skeleton, as Sans reeled. They both stood in stillness by Sans’s old sentry post at the entry to Hotlands. The lava still bubbled and lapped at charred rock. Sans smiled.

“it’s been a pretty long _time_ , gaster.”

“Ever the comedian.” Gaster chuckled politely, arms folding. Sans shrugged and grinned, offering Gaster a dry laugh. “I suppose I know why you’re here. I do have to ask why you’d bother.”

“i’m not letting you get away with all this. i’ve seen too many resets, too many possibilities to give anything up now. i used to really not care. but now that everyone’s free? i can’t afford to lose it all.” Sans stood firmly in front of Gaster, who was uttering a chuckle.

“You certainly have changed, Sans. Tell me how you intend to take the human from me, exactly. I was the one who taught you what you have. There is no fighting me, Sans. You cannot fight what technically does not even exist. Surely you must know this better than others.” Gaster’s pupils flared at the surge of magic rippling through Sans. One blue pupil burned as Sans glowered at the scientist. Yet the smile never left his face, only now it seemed spiteful.

“if there’s no convincing you otherwise, then fightin’ is all i’ve got left. i’m not leaving.” Not without you. 

“The human is happier here. I have arranged for it to be so. I have experiments to run. Science does not wait. Leave, before I am forced to take matters into my own hands.” Gaster warned, irritated. The smile on his face had begun to slip, wanting to get rid of Sans. It was too risky to try and erase him without thought. It could affect your mind, and Gaster would prefer to avoid such an issue. 

Sans shrugged, winking. He didn’t believe Gaster. He couldn’t win, he couldn’t fight against the one thing that controlled time itself on withered fingertips. Gaster frowned, before hands clasped behind his back.

“I am giving you this chance to leave, Sans. I am not without mercy, after all. Do not make me have to fight you.”

Sans had let his eye flare, hoping to catch Gaster off guard. He felt the world shift under his feet as he fell, hitting the ground outside of Mount Ebott. He cursed as he stood, trying to slice open a door, his arm burning in pain as the rip forced itself closed. 

“ _fuck_.” Sans spat, smile twitching. He needed a plan. Something. He was strong enough to make it on his own, he would keep working. If Gaster wanted to play smart, then so would he. 

You had read the note, settling on eating and watching DVDs, having a shower and killing time, until the burst of air had you smiling, getting used to the white noise in your ears.

“Hey, Gaster. Did you get your samples?”

His eyes flickered in momentary confusion, before he realised. 

“Ah, yes. I have already ported them to the lab. Magic is convenient that way.” He chuckled, and you hummed softly, feeling strangely sluggish. “How are you feeling, human, any better?”

“I think so. I’ll forget about it, soon.” You chuckled. Gaster smiled, too.

You didn’t know how truthful your words were going to be.

**Notes for the Chapter:**

> It'll be kind of like that feeling you get when you walk into a room and forget why you've gone in. Only with an entire existence. Creepy.


	12. Carriwitchet

**Notes for the Chapter:**

> Sorry for the slight delay with this chapter! I had been drafting it forever, but now it's up and I can start to flood them out again!   
> Also, I've been thinking about making another multi-chapter fic (yes, yes, greedy, I know.) and whilst I won't stop updating this, I might actually put the plan in motion. Thank you ever so much for enjoying the fic, I adore your comments (even if I never reply because I'm /awful/) and I hope you enjoy reading! 
> 
> Also please hit me up on Tumblr because I'm very small and lovely I promise <3 @undertrailingbehind

“Say ‘ah’.”

Gaster smiled as you complied. Something slid along your tongue, gathering samples and noting down in a careful tranquility. He was pleased to see you comply so easily. He applied gentle pressure to your throat, asking you to swallow as he watched your insides twitch and tense, your open mouth panting softly.

“Very good. Forgive me if this is uncomfortable for you.” Your mouth was allowed to close, and you smiled slowly. 

“It’s not.”

You were so relaxed. The timeline had bled into you, luckily. But Gaster was intent to remove your previous timeline entirely. Have it disposed of, have it replaced. You would be fine. Gaster had finished his tests for the day, letting you go as you plodded up to him, smiling. He returned the expression with an added chuckle, skeletal fingers ran along your scalp in comfort.

“Can I ask you something, Gaster?”

“You are always free, you know this.” He smiled, as he ushered you towards the elevator shaft, hands lifting you carefully as he joined you, taking your hand and leading you to your bed, sitting you down. You pondered over the wording of your question, before coming to some kind of resolution within yourself, shuffling to leave a leg on the bed, one safely on the ground as you fully faced Gaster.

“Have you always been into science? I can’t imagine you doing much else, to be honest.” You giggled softly, as he smiled in such a weaker, quieter way. His pupils flickered and he gazed at his coat pensively.

“I have always had a passion for science, yes. I had to figure out how everything worked, down to every detail. Not much has changed, seemingly. I still desire to research the world. I simply _have_ to know.” He explained as fingers picked at specks on the fabric of his clothes.

“I guessed as much. It’s pretty cute.” You laughed as he turned, a greenish tint seeping into his pupils as he chuckled softly. 

“It’s rather dull, admittedly. I lost a good amount of friendships due to my constant pursuit of knowledge. Sometimes I wonder how differently I could have become if I had stopped burning with such a heavy desire to simply know.” He spoke truthfully, as you shuffled closer, taking a bony hand in your own, feeling soft pricks of magic tickle your palms.

“...I’m glad you stuck with it.”

You murmured sweetly. He almost felt guilty for doing these things to you. For changing you to be this, just for the sake of him. You weren’t hurt, but Gaster knew better than to assume that no physical pain meant that everything was okay. He was a prime example of falling apart under the surface. He laughed, before you were leaning up to peck his cracked cheek, fingers sliding to stroke along his cervical vertebrae, dipping under the collar of his sweater, smiling as he twitched.

He looked so intimidating, hovering over you as you lay on your back, pupils burning brightly as he gazed into your half lidded eyes, fingers ghosting along the soft fabric of your underwear, testing the give in the cotton, pressing into your folds and rubbing in curiosity, watching you buck your hips, searching for more attention.

“Would you like to continue?” He smiled at you as you deadpanned, half wondering if you should cross your arms and outright pout at him. He chuckled, leaning back to rest on his knees, tugging your panties off and admiring the soft skin newly uncovered. 

You tugged his coat to come back down, a tongue slid out to press inside of your mouth, pulsating and curling tightly around your own, angling your hips up to grind against Gaster’s lap, whining into his open mouth, you silently urged for more, breaking the kiss to pant for air, swallowing in the warmth surrounding you, Gaster dipped his head to lap at your neck. A prickling numbness radiated along oddly wet flesh, as fingers finally started to push inside of you, feeling your insides tense as bones curled and fucked you. 

“G-Gaster...could you g-go down on me…?” As soon as you had asked, you felt shy, unable to close your legs, simply tensing your thighs around Gaster’s own, fingers paused and rested inside you, as he looked towards you.

“If you show me what to do, I do not see the harm.”

You wriggled your back slightly, before you felt his fingers slip out of you, feeling an odd coolness on your wet labia, before you were gently pushing his skull down. He seemed to take the hint, his head neatly between your legs as he gazed up at you, inspecting your parts up close. He pulled on your clitoral hood and rubbed it, exposing the firm little nub with a pleased smile.

“I must research this further, human. It is a very endearing bundle of nerves.” He chuckled as you squirmed, watching the way you tensed and groaned, your arm slinging over your mouth to stifle the soft strings of moans oozing from covered lips. 

He wondered what you tasted like. Perhaps sweet, the pink wetness of your flesh looked as such. His tongue gave an experimental lick along your lips and watched you arch your back, desperate for the feeling. His tongue oozed magic along your folds as he ghosted it along once more, before humming in thought. Hands out of view jotted notes in silence. There was much you could teach him.

“Keep doing that, Gaster…” You breathed, your arm moving from your mouth to speak, gazing down at the scientist, your cheeks warm as you watched him glance up for a moment, smiling. His tongue slowly slipped out, throbbing green as he lowered himself, lapping at your clit, slipping down to press against your hole, before you felt the strange thrum of magic push inside of you.

It squirmed, squeezing in and out and unlike anything you had ever felt inside of you. Your toes curled and your hips rolled as you tried to lift to have his tongue in deeper. You felt your breath hitch as a phantom pair of hands held your ribs carefully, kneading the flesh gently as you were urged forward slightly, complying as he pressed a finger inside, his tongue and phalanges working your insides.

You were coming, short huffs of breath alerted you as a hot heat started twitching in your muscles, your head lolling back to sink into the pillow behind you, fingers now gripped the back of Gaster’s head, grinding yourself into him as his tongue awkwardly tried to keep up, pupils flaring in surprise as you rode his face, forcing him as close as possible, you felt bony fingers against your clit, pinching delicately before you gasped in the cool air, your eyes screwing shut as your orgasm fluttered between your legs.

Gaster had let you grind it out, his mouth slick with your wetness, once you had loosened your grip, he sat up, his tongue poking out to prod the corners of his mouth, smiling sheepishly at you.

“Well, that was quite the reaction.” He chuckled, his voice echoed in your skull as you offered him a weak laugh, slightly breathless. 

“That was...really good.” You wheezed softly, and he laughed, slipping off of the bed to loom over you by your side, pressing a hand to your forehead and gauging your temperature. Your own hand came to stroke his fingers. You smiled.

“Is something amusing, human?” He chuckled.

“I feel so good.” You mumbled with a giggle. Your afterglow was settling in, and you stifled a soft yawn as you gazed up at Gaster, who had summoned hands to pull the blanket from under you, shifting you about until you looked comfortable.

He was happy. You were feeling good. He could start to slowly get rid of the other timeline. He could afford to have you forget, knowing you were comforted and contented. 

He could remove _Sans_. There would be no more issue. Gaster was excited to test out his theories of timeline manipulation. Could he truly remove everything from one life and force another into you? He wondered how permanent it would be, but with enough calculating it should be stable forever. Ideas buzzed through his mind, so much so that he hadn’t noticed your hand slip from the covers, firmly grasping his wrist.

“...Is it okay if I sleep for a while?”

“Of course, human. Please, rest well.” He smiled down at you, his free hand coming to stroke your hair, as you hummed softly.

“Don’t work too hard.”

He chuckled, your grip left him, and he slowly wandered off.

He hadn’t thought of it before, but perhaps even he was different in your timeline. He had taken it apart, reconstructed, and pasted it where it was needed. Gaster felt like an imposter, somehow. He huffed a haughty sigh, hands slowly emerging as they clutched notes and pencils, scribbling.

The true lab was dim, the hum of machines were the only thing ebbing the silence. Gaster looked over your phone, missed calls flashing from names he had never heard you speak. He saw Alphys, and pulled a face.

“I should test my theory on deleting memories. Perhaps I should pick a name from here.” He mused. Removing Sans from your memories so swiftly might be damaging. Though, the same threat lingered with anyone. He sighed. 

He brought up a piece of paper, looking it over. Details of the timeline he had plucked and ripped apart, replacing and layering over. The one where you and him had been more than flashes of fearful conversation. _Friends_ , even. Gaster smiled fondly, as if he himself recalled the memories, despite them never truly happening.

He had destroyed a timeline. Blurred the lines of reality and existence, all of the science was planned behind your back, and he worked tirelessly to ensure you neither knew or cared to know. He prodded at the paper, before jotting down a small note.

“Subject has expressed happiness and a relaxed state. This enough is consent to carry on further tests on timeline manipulation. I will start by altering and removing memories of friends. If this should fail, I will hope to fabricate a substitute memory to placate the subject.” Gaster spoke as hands wrote just as quickly. He couldn’t hope to get rid of Sans quite yet. Not when the annoying little prick was making Gaster so paranoid.

Sans had been fuming. Fury was a gross understatement, eye raging storms in his socket as he stormed his way into Alphys’s new surface workplace, his smile strained and lopsided.

“gaster caught me. better yet, he’s pretty damn aware of me tryin’ to get in for now. i need you to help me get into the underground without using any magic. i have to get her back.” Sans had settled enough to look miserable. Alphys adjusted her glasses and frowned. 

“H-How do you think we’ll even be able to d-do it?” Alphys tugged on her lab coat, shuffling to stand and eye Sans. Alphys had only ever heard conjecture about Gaster, never complete facts. To attempt to fight an entity that did not even wholly exist was beyond the realm of thought. She sighed, feeling hopeless. 

“we have to do _something_. listen, i’m the last person who wants to do anything ever, you know? but gaster has way more power than you think he does,” Sans knew. The power to control resets. His phantom stomach knotted and churned at the idea that everything he had finally grown to love, including you, would be snatched. He’d wake up in Snowdin, his brother would be shouting for him to get ready. The thought made him truly ill. “if we don’t stop him, he might really fuck everything up.” 

“O-Okay. I could start m-maybe planning tonight, and-”

“i need it pretty fast. we don’t really have the time to spare.”

Alphys began to sweat, feeling pressure building in her spine, she fiddled with the buttons on her coat and fumbled nervously. She didn’t understand as much as Sans. But the idea of Gaster having enough power to start affecting time on a global scale was enough to drive her into action. Sans watched the gears turn in her head, eyes wandered to her desk.

“I-It won’t be perfect, but I have an idea.”

“i’ll take it.”

**Author's Note:**

> Thank you for reading! You can catch me on Tumblr at undertrailingbehind <3


End file.
